gpu: drm: Replace bare "unsigned" with "unsigned int"

Replaced the type "unsigned" with "unsigned int" because it is
preferred. Issue detected by checkpatch.pl.

Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210412105309.27156-1-fmdefrancesco@gmail.com