drm/i915/dsb: Enable programmable DSB interrupt

drm/i915/dsb: Enable programmable DSB interrupt

The DSB can signal a programmable interrupt in response to
a specific DSB command getting executed. Hook that up.

For now we'll just use this to signal the completion of the
commit via a vblank event. If, in the future, we'll need to
do other things in response to DSB interrupts we may need to
come up with some kind of fancier DSB interrupt framework where
the caller can specify a custom handler...

Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240930170415.23841-5-ville.syrjala@linux.intel.com