Include <linux/vmalloc.h> in fbdev emulation to get vzalloc() and
vfree() on MIPS. The error messages are shown below and bug reports
are at [1] and [2].

  drivers/gpu/drm/drm_fbdev_generic.c: In function 'drm_fbdev_cleanup':
  drivers/gpu/drm/drm_fbdev_generic.c:63:17: error: implicit declaration of function 'vfree'; did you mean 'kvfree'? [-Werror=implicit-function-declaration]
     63 |                 vfree(shadow);
        |                 ^~~~~
        |                 kvfree
  drivers/gpu/drm/drm_fbdev_generic.c: In function 'drm_fbdev_fb_probe':
  drivers/gpu/drm/drm_fbdev_generic.c:219:38: error: implicit declaration of function 'vzalloc'; did you mean 'kvzalloc'? [-Werror=implicit-function-declaration]
    219 |                 fbi->screen_buffer = vzalloc(fbi->screen_size);
        |                                      ^~~~~~~
        |                                      kvzalloc
  drivers/gpu/drm/drm_fbdev_generic.c:219:36: warning: assignment to 'char *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
    219 |                 fbi->screen_buffer = vzalloc(fbi->screen_size);

Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 8ab59da26bc0 ("drm/fb-helper: Move generic fbdev emulation into separate source file")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Link: https://lore.kernel.org/dri-devel/202211060911.5U76gMtE-lkp@intel.com/T/#u # [1]
Link: https://lore.kernel.org/dri-devel/202211060331.1SoD1tAR-lkp@intel.com/T/#u # [2]
Link: https://patchwork.freedesktop.org/patch/msgid/20221107125329.12842-2-tzimmermann@suse.de

Move the generic fbdev implementation into its own source and header
file. Adapt drivers. No functional changes, but some of the internal
helpers have been renamed to fit into the drm_fbdev_ naming scheme.

v3:
	* rename drm_fbdev.{c,h} to drm_fbdev_generic.{c,h}
	* rebase onto vmwgfx changes
	* rebase onto xlnx changes
	* fix include statements in amdgpu

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221103151446.2638-22-tzimmermann@suse.de