drm/i915/psr: Define more PSR mask bits

drm/i915/psr: Define more PSR mask bits

Define more of the PSR mask bits, and describe in detail
what some of them do. Even if we don't set them all from
the driver they can be very useful during PSR debugging.
Having to trawl through bspec every time to find them is
not fun, and re-reverse engineering the behaviour every
time is time consuming (even if a bit more fun than spec
trawling).

v2: Moar bits
    Put the description into a comment to be easily available
v2: Fix the BDW_UNMASK_VBL_TO_REGS_IN_SRD/HSW_UNMASK_VBL_TO_REGS_IN_SRD
    description
    Rebase due to intel_psr_regs.h

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230411191429.29895-6-ville.syrjala@linux.intel.com
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>