drm/i915/fbc: Introduce .nuke() vfunc

Eliminate yet another if-ladder by adding .nuke() vfunc.

We also rename all *_recompress() stuff to *_nuke() since
that's the terminology the spec uses. Also "recompress"
is a bit confusing by perhaps implying that this triggers
an immediate recompression. Depending on the hardware that
may definitely not be the case, and in general we don't
specifically know when the hardware decides to compress.
So all we do is "nuke" the current compressed framebuffer
and leave it up to the hardware to recompress later if it
so chooses.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211104144520.22605-8-ville.syrjala@linux.intel.com


Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>