drm/mga/mga_dma: Demote kernel-doc abusers to standard comment blocks

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/mga/mga_dma.c:29: warning: Cannot understand  * file mga_dma.c
 drivers/gpu/drm/mga/mga_dma.c:455: warning: Function parameter or member 'dev' not described in 'mga_do_agp_dma_bootstrap'
 drivers/gpu/drm/mga/mga_dma.c:455: warning: Function parameter or member 'dma_bs' not described in 'mga_do_agp_dma_bootstrap'
 drivers/gpu/drm/mga/mga_dma.c:629: warning: Function parameter or member 'dev' not described in 'mga_do_pci_dma_bootstrap'
 drivers/gpu/drm/mga/mga_dma.c:629: warning: Function parameter or member 'dma_bs' not described in 'mga_do_pci_dma_bootstrap'
 drivers/gpu/drm/mga/mga_dma.c:1150: warning: Function parameter or member 'dev' not described in 'mga_driver_unload'
 drivers/gpu/drm/mga/mga_dma.c:1159: warning: Function parameter or member 'dev' not described in 'mga_driver_lastclose'

Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: by <jhartmann@precisioninsight.com>
Cc: Faith <faith@valinux.com>
Cc: Jeff Hartmann <jhartmann@valinux.com>
Cc: Keith Whitwell <keith@tungstengraphics.com>
Cc: Gareth Hughes <gareth@valinux.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201106214949.2042120-5-lee.jones@linaro.org

drivers/gpu/drm/mga/mga_dma.c

@@ -25,7 +25,7 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
-/**
+/*
  * \file mga_dma.c
  * DMA support for MGA G200 / G400.
  *
@@ -435,7 +435,7 @@ int mga_driver_load(struct drm_device *dev, unsigned long flags)
 }
 
 #if IS_ENABLED(CONFIG_AGP)
-/**
+/*
  * Bootstrap the driver for AGP DMA.
  *
  * \todo
@@ -610,7 +610,7 @@ static int mga_do_agp_dma_bootstrap(struct drm_device *dev,
 }
 #endif
 
-/**
+/*
  * Bootstrap the driver for PCI DMA.
  *
  * \todo
@@ -1143,7 +1143,7 @@ int mga_dma_buffers(struct drm_device *dev, void *data,
 	return ret;
 }
 
-/**
+/*
  * Called just before the module is unloaded.
  */
 void mga_driver_unload(struct drm_device *dev)
@@ -1152,7 +1152,7 @@ void mga_driver_unload(struct drm_device *dev)
 	dev->dev_private = NULL;
 }
 
-/**
+/*
  * Called when the last opener of the device is closed.
  */
 void mga_driver_lastclose(struct drm_device *dev)