drm/i915/dmc: Hook up PIPEDMC interrupts

drm/i915/dmc: Hook up PIPEDMC interrupts

Hook up PIPEDMC interrupts. We'll need these for:
- flip queue signalling
- GTT/ATS faults on LNL+
- unclaimed register access errors (supposedly that is what
  the error interrupt indicated according to Windows code).

On LNL+ we get a new level of interrupts registers PIPEDMC_INTERRUPT*.
On earlier platforms we only have the INT_VECTOR field in the
PIPEDMC_STATUS registers, whose values are defined by the firmware.

For now we'll enable the interrupts on LNL+ only. For earlier platforms
it's not clear that there is any use for these interrupts, and some
ADL machines have exhibited spurious DE_PIPE interrupts with the
PIPEDMC interrupts unmasked/enabled. We can revisit enabling these
for earlier platforms in the future.

For some unknown reason LNL pipe B triggers the error interrupt
during the first DC state transition (subsequent transitions are
maybe OK?). No clear idea what's going on here yet, so keep the
error interrupt disabled for now.

Similar to DSB interrupt registers, the unused bits in
PIPEDMC_INTERRUPT* seem to act like randomg r/w bits (instead
of being hardwired to 0 like one would expect), and so we'll try
to avoid setting them so that we don't mistake them for real
interrupts.

v2: Only enable/unmask for LNL+
    Keep the flip queue interrupt masked off for now since
    we don't have a use for it yet
v3: Also keep the error interrupt masked off for now due to
    LNL pipe B triggering it

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250514174257.8708-1-ville.syrjala@linux.intel.com