drm/i915: Define the PIPE_CRC_EXP registers

I need a scratch register which fill the following requirements:
- can be accessed via DSB
- all the bits can be read/written
- no serious side effects

So far the only thing I could think of is the "expected CRC"
register. Add the definition so I can use it.

While I only need the hsw+ variant currently, let's define the
older variants as well for completeness.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240531115342.2763-7-ville.syrjala@linux.intel.com


Acked-by: Jani Nikula <jani.nikula@intel.com>