drm/i915: Update IP_VER(12, 50)

drm/i915: Update IP_VER(12, 50)

With no platform using graphics/media IP_VER(12, 50), replace the
checks throughout the code with IP_VER(12, 55) so the code makes sense
by itself with no additional explanation of previous baggage.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Tvrtko Ursulin <tursulin@ursulin.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20240320060543.4034215-5-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>