drm/i915/uc: fetch uc firmwares for each GT

The FW binaries are independently loaded on each GT. On MTL, the memory
is shared so we could potentially re-use a single allocation, but on
discrete multi-gt platforms we are going to need independent copies,
so it is easier to do the same on MTL as well, given that the amount
of duplicated memory is relatively small (~500K).

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: John Harrison <john.c.harrison@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221108020600.3575467-2-daniele.ceraolospurio@intel.com