drm/exynos: use arch independent types in uapi header

User API structs should not use types which size/alignment/padding depends
on architecture. The patch fixes it for all structures except
drm_exynos_g2d_userptr, as g2d related stuff seems to be more complicated
and will be reviewed/adjusted later.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>