drm/i915/fbc: Allocate llb before cfb

Since the llb allocation has a fixed size, let's grab it before
the potentially variable sized cfb. That should avoid some allocation
failure cases once we allow different compression ratios for FBC1.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210610183237.3920-10-ville.syrjala@linux.intel.com


Reviewed-by: José Roberto de Souza <jose.souza@intel.com>