drm: direct include of drm.h in drm_gem_shmem_helper.c

Do not rely on including drm.h from drm_file.h,
as the include in drm_file.h will be dropped.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Sean Paul <sean@poorly.run>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Eric Anholt <eric@anholt.net>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190718161507.2047-8-sam@ravnborg.org

drivers/gpu/drm/drm_gem_shmem_helper.c

@@ -10,6 +10,7 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 
+#include <drm/drm.h>
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_gem_shmem_helper.h>