drm/i915/mtl/gsc: Add a gsc_info debugfs

Add a new debugfs to dump information about the GSC. This includes:

- the FW path and SW tracking status;
- the release, security and compatibility versions;
- the HECI1 status registers.

Note that those are the same registers that the mei driver dumps in
their own status sysfs on DG2 (where mei owns the GSC).

To make it simpler to loop through the status register, the code has
been update to use a PICK macro and the existing code using the regs had
been adapted to match.

v2: fix includes and copyright dates (Alan)
v3: actually fix the includes

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230612181529.2222451-5-daniele.ceraolospurio@intel.com