drm/stm: Use drm_gem_fb_create()

drm/stm: Use drm_gem_fb_create()

drm_fb_cma_create() is just a wrapper around drm_gem_fb_create() now,
so use the function directly.

Cc: Yannick Fertre <[email protected]>
Cc: Philippe Cornu <[email protected]>
Cc: Benjamin Gaignard <[email protected]>
Cc: Vincent Abriou <[email protected]>
Signed-off-by: Noralf Trønnes <[email protected]>
Acked-by: Philippe Cornu <[email protected]>
Tested-by: Philippe Cornu <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]