drm/vkms: Remove useless drm_rotation_simplify

As all the rotation are now supported by VKMS, this simplification does
not make sense anymore, so remove it.

Acked-by: Maíra Canal <mairacanal@riseup.net>
Reviewed-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241118-yuv-v14-9-2dbc2f1e222c@bootlin.com


Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>