drm/i915: stick to kernel fixed size types

We no longer allow mixed C99 and kernel types, and the preference is to
use kernel types exclusively. Fix the C99 types that have crept in since
the mass conversion. No functional changes.

Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Cc: Kevin Strasser <kevin.strasser@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Swati Sharma <swati2.sharma@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190318160019.9309-1-jani.nikula@intel.com