drm/xe/gsc: add support for GSC proxy interrupt

The GSC notifies us of a proxy request via the HECI2 interrupt. The
interrupt must be enabled both in the HECI layer and in our usual gt irq
programming; for the latter, the interrupt is enabled via the same enable
register as the GSC CS, but it does have its own mask register. When the
interrupt is received, we also need to de-assert it in both layers.

The handling of the proxy request is deferred to the same worker that we
use for GSC load. New flags have been added to distinguish between the
init case and the proxy interrupt.

v2: rename irq define, fix include ordering (Alan)

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240117182621.2653049-3-daniele.ceraolospurio@intel.com

drm/xe/gsc: Initialize GSC proxy

The GSC uC needs to communicate with the CSME to perform certain
operations. Since the GSC can't perform this communication directly on
platforms where it is integrated in GT, the graphics driver needs to
transfer the messages from GSC to CSME and back. The proxy flow must be
manually started after the GSC is loaded to signal to GSC that we're
ready to handle its messages and allow it to query its init data from
CSME.

Note that the component must be removed before the pci_remove call
completes, so we can't use a drmm helper for it and we need to instead
perform the cleanup as part of the removal flow.

v2: add function documentation, more targeted memory clear, clearer logs
and variable names (Alan)

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240117182621.2653049-2-daniele.ceraolospurio@intel.com