Revert "drm/i915/display/fbc: Disable fbc by default on TGL"

FBC can be re-enabled on TGL with WA of keeping it disabled
while PSR2 is enabled.

This reverts commit 2982ded2.

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201201190406.1752-3-uma.shankar@intel.com