drm/i915/gt: Extract function to apply media fuses

Just like is done for compute and copy engines, extract a function to
handle media engines. While at it, be consistent on using or not the
uncore/gt/info variable aliases.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220909-media-v2-2-6f20f322b4ef@intel.com