drm/i915/pxp/mtl: Update pxp-firmware response timeout

Update the max GSC-fw response time to match updated internal
fw specs. Because this response time is an SLA on the firmware,
not inclusive of i915->GuC->HW handoff latency, when submitting
requests to the GSC fw via intel_gsc_uc_heci_cmd_submit helpers,
start the count after the request hits the GSC command streamer.
Also, move GSC_REPLY_LATENCY_MS definition from pxp header to
intel_gsc_uc_heci_cmd_submit.h since its for any GSC HECI packet.

Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Reviewed-by: Vivaik Balasubrawmanian <vivaik.balasubrawmanian@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230917211933.1407559-2-alan.previn.teres.alexis@intel.com