drm/i915/uc: More refactoring of UC version numbers

As a precursor to a coming change (for adding a GuC submission API
version), abstract the UC version number into its own private
structure separate to the firmware filename.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221129232031.3401386-3-John.C.Harrison@Intel.com