drm/i915: Polish types in fb calculations

drm/i915: Polish types in fb calculations

Be a bit more consistent in our use of integer types in
the fb related calculatiosn. u32 we generally only use
for ggtt offsets and such, and everything else can be regular
(unsigned) ints.

There's also an overabundance of consts for local variables
in skl_check_main_surface() which is not something we generally
do. So get rid of those while at it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240506125718.26001-6-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>