drm/i915/psr: Make MASK_DISP_REG_WRITE reserved in PSR_MASK for ICL

drm/i915/psr: Make MASK_DISP_REG_WRITE reserved in PSR_MASK for ICL

ICL spec states that this bit is now reserved.

Bspec: 7722

v2(Dhinakaran and Jani):
- instead of remove bit in gen11 now only setting if if gen < 11
- changed commit title

Cc: Jani Nikula <[email protected]>
Reviewed-by: Dhinakaran Pandiyan <[email protected]>
Signed-off-by: José Roberto de Souza <[email protected]>
Signed-off-by: Dhinakaran Pandiyan <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]