Remove the old tales about 90/270 degree rotation
effectively preventing FBC. That hasn't been true since
we stopped demanding the fence is present in
commit 691f7ba5 ("drm/i915/display/fbc: Make fences
a nice-to-have for GEN9+")

Also fix up the multiline comment formatting while at it.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220916165206.1499-2-ville.syrjala@linux.intel.comReviewed-by: Luca Coeho <luciano.coelho@intel.com>