drm/i915/psr: Implement WaPsrDPAMaskVBlankInSRD:hsw

drm/i915/psr: Implement WaPsrDPAMaskVBlankInSRD:hsw

Implement WaPsrDPAMaskVBlankInSRD:hsw, which makes the hardware
generate the extra vblank between link training and first frame
being transmitted. This is the same thing that's controlled by
TRANS_CHICKEN[21] on skl+ (but due to the funky double buffering
it's effectively always at the rest value after DC5 exit). So
for consistent behaviour we want every platform to generate said
vblank. BDW is already setting this up correctly.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230609141404.12729-9-ville.syrjala@linux.intel.com
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>