The code assumes we can omit the cfb allocation once fbc
has been enabled once. That's nonsense. Let's try to
reallocate it if we need to.

The code is still a mess, but maybe this is enough to get
fbc going in some cases where it initially underallocates
the cfb and there's no full modeset to fix it up.

Cc: Daniel Drake <drake@endlessm.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Jian-Hong Pan <jian-hong@endlessm.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191127201222.16669-15-ville.syrjala@linux.intel.comTested-by: Daniel Drake <drake@endlessm.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>