drm/i915: s/int/u32/ for aux_offset/alignment

ggtt offsets/alignments are u32 everywhere else. Don't use
a signed int for them here.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201008101608.8652-3-ville.syrjala@linux.intel.com


Reviewed-by: Imre Deak <imre.deak@intel.com>