drm/fbdev: Include <linux/vmalloc.h>

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 <[email protected]>
Acked-by: Daniel Vetter <[email protected]>
Signed-off-by: Thomas Zimmermann <[email protected]>
Fixes: 8ab59da ("drm/fb-helper: Move generic fbdev emulation into separate source file")
Cc: Thomas Zimmermann <[email protected]>
Cc: Javier Martinez Canillas <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Maxime Ripard <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/dri-devel/[email protected]/T/#u # [1]
Link: https://lore.kernel.org/dri-devel/[email protected]/T/#u # [2]
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: Thomas Zimmermann

drivers/gpu/drm/drm_fbdev_generic.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MIT
 
 #include <linux/moduleparam.h>
+#include <linux/vmalloc.h>
 
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_drv.h>