staging: most: add SPDX identifiers to all most driver files

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the drivers/staging/most files files with the correct SPDX
license identifier based on the license text in the file itself.  The
SPDX identifier is a legally binding shorthand, which can be used
instead of the full boiler plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Michael Fabry <Michael.Fabry@microchip.com>
Cc: Christian Gromm <christian.gromm@microchip.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/aim-cdev/cdev.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * cdev.c - Application interfacing module for character devices
  *

drivers/staging/most/aim-network/networking.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Networking AIM - Networking Application Interface Module for MostCore
  *

drivers/staging/most/aim-sound/sound.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * sound.c - Audio Application Interface Module for Mostcore
  *

drivers/staging/most/aim-v4l2/video.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * V4L2 AIM - V4L2 Application Interface Module for MostCore
  *

drivers/staging/most/hdm-dim2/dim2_errors.h

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dim2_errors.h - Definitions of errors for DIM2 HAL API
  * (MediaLB, Device Interface Macro IP, OS62420)

drivers/staging/most/hdm-dim2/dim2_hal.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dim2_hal.c - DIM2 HAL implementation
  * (MediaLB, Device Interface Macro IP, OS62420)

drivers/staging/most/hdm-dim2/dim2_hal.h

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dim2_hal.h - DIM2 HAL interface
  * (MediaLB, Device Interface Macro IP, OS62420)

drivers/staging/most/hdm-dim2/dim2_hdm.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dim2_hdm.c - MediaLB DIM2 Hardware Dependent Module
  *

drivers/staging/most/hdm-dim2/dim2_hdm.h

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dim2_hdm.h - MediaLB DIM2 HDM Header
  *

drivers/staging/most/hdm-dim2/dim2_reg.h

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dim2_reg.h - Definitions for registers of DIM2
  * (MediaLB, Device Interface Macro IP, OS62420)

drivers/staging/most/hdm-dim2/dim2_sysfs.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dim2_sysfs.c - MediaLB sysfs information
  *

drivers/staging/most/hdm-dim2/dim2_sysfs.h

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dim2_sysfs.h - MediaLB sysfs information
  *

drivers/staging/most/hdm-i2c/hdm_i2c.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * hdm_i2c.c - Hardware Dependent Module for I2C Interface
  *

drivers/staging/most/hdm-usb/hdm_usb.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * hdm_usb.c - Hardware dependent module for USB
  *

drivers/staging/most/mostcore/core.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * core.c - Implementation of core module of MOST Linux driver stack
  *

drivers/staging/most/mostcore/mostcore.h

+// SPDX-License-Identifier: GPL-2.0
 /*
  * mostcore.h - Interface between MostCore,
  *   Hardware Dependent Module (HDM) and Application Interface Module (AIM).