staging: emxx_udc: Remove EMMA Mobile USB Gadget driver

No one stepped up to complete the EMMA Mobile USB Gadget driver, bring
it up to non-staging standards, and convert it to device tree.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Link: https://lore.kernel.org/r/c7bc2c95458f9710e043cbedee4270dd41fcae29.1705932585.git.geert+renesas@glider.beSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/Kconfig

@@ -46,8 +46,6 @@ source "drivers/staging/iio/Kconfig"
 
 source "drivers/staging/sm750fb/Kconfig"
 
-source "drivers/staging/emxx_udc/Kconfig"
-
 source "drivers/staging/nvec/Kconfig"
 
 source "drivers/staging/media/Kconfig"

drivers/staging/Makefile

@@ -14,7 +14,6 @@ obj-$(CONFIG_VT6656)		+= vt6656/
 obj-$(CONFIG_VME_BUS)		+= vme_user/
 obj-$(CONFIG_IIO)		+= iio/
 obj-$(CONFIG_FB_SM750)		+= sm750fb/
-obj-$(CONFIG_USB_EMXX)		+= emxx_udc/
 obj-$(CONFIG_MFD_NVEC)		+= nvec/
 obj-$(CONFIG_STAGING_BOARD)	+= board/
 obj-$(CONFIG_LTE_GDM724X)	+= gdm724x/

drivers/staging/emxx_udc/Kconfig

-# SPDX-License-Identifier: GPL-2.0
-config USB_EMXX
-	tristate "EMXX USB Function Device Controller"
-	depends on USB_GADGET && (ARCH_RENESAS || COMPILE_TEST)
-	help
-	   The Emma Mobile series of SoCs from Renesas Electronics and
-	   former NEC Electronics include USB Function hardware.
-
-	   Say "y" to link the driver statically, or "m" to build a
-	   dynamically linked module called "emxx_udc" and force all
-	   gadget drivers to also be dynamically linked.

drivers/staging/emxx_udc/Makefile

-# SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_USB_EMXX)	:= emxx_udc.o

drivers/staging/emxx_udc/TODO

-* add clock framework support (platform device with CCF needs special care)
-* break out board-specific VBUS GPIO to work with multiplatform
-* convert VBUS GPIO to use GPIO descriptors from <linux/gpio/consumer.h>
-  and stop using the old GPIO API
-* DT bindings
-* move driver into drivers/usb/gadget/