drm/i915/pxp: Add GSC-CS backend to send GSC fw messages

Add GSC engine based method for sending PXP firmware packets
to the GSC firmware for MTL (and future) products.

Use the newly added helpers to populate the GSC-CS memory
header and send the message packet to the FW by dispatching
the GSC_HECI_CMD_PKT instruction on the GSC engine.

We use non-priveleged batches for submission to GSC engine
which require two buffers for the request:
     - a buffer for the HECI packet that contains PXP FW commands
     - a batch-buffer that contains the engine instruction for
       sending the HECI packet to the GSC firmware.

Thus, add the allocation and freeing of these buffers in gsccs
init and fini.

The GSC-fw may reply to commands with a SUCCESS but with an
additional pending-bit set in the reply packet. This bit
means the GSC-FW is currently busy and the caller needs to
try again with the gsc_message_handle the fw returned. Thus,
add a wrapper to continuously retry send_message while
replaying the gsc_message_handle. Retries need to follow the
arch-spec count and delay until GSC-FW replies with the real
SUCCESS or timeout after that spec'd delay.

The GSC-fw requires a non-zero host_session_handle provided
by the caller to enable gsc_message_handle tracking. Thus,
allocate the host_session_handle at init and destroy it
at fini (the latter requiring an FYI to the gsc-firmware).

Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230511231738.1077674-5-alan.previn.teres.alexis@intel.com