drm/amd/display: fbc state could not reach while enable fbc

   [WHY] fbc is within the data path from memory to dce. while
   re-configure mc dmif, fbc should be enabled. otherwise, fbc
   may not be enabled properly.

   [HOW] before re-configure mc dmif, disable fbc, only after
   dmif re-configuration fully done, enable fbc again.

Signed-off-by: hersen wu <hersenxs.wu@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>