drm/i915/guc: Extract param logic form guc_init_fw()

Let intel_guc_init_fw() focus on determining and fetching the correct
firmware.

This patch introduces intel_uc_sanitize_options() that is called from
intel_sanitize_options().

Then, if we have GuC, we can call intel_guc_init_fw() conditionally
and we do not have to do the internal checks.

v2: fix comment, notify when nuking GuC explicitly enabled (M. Wajdeczko)
v3: fix comment again, change the nuke message (M. Wajdeczko)
v4: update title to reflect new function name + rebase
v5: text && remove 2 uneccessary checks (M. Wajdeczko)

Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>