drm/i915/adlp/fb: Remove restriction on semiplanar UV plane offset

Since the surfaces of tiled FBs on ADLP are remapped it's pointless to
require an alignment in the allocated object. The necessary tile-row
alignment (to be programmed to the surface start register) will be
ensured later when flipping to the FB.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211026225105.2783797-7-imre.deak@intel.com