drm/i915/adlp/fb: Prevent the mapping of redundant trailing padding NULL pages

So far the remapped view size in GTT/DPT was padded to the next aligned
offset unnecessarily after the last color plane with an unaligned size.
Remove the unnecessary padding.

Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Fixes: 3d1adc3d ("drm/i915/adlp: Add support for remapping CCS FBs")
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/20211026225105.2783797-3-imre.deak@intel.com