gfx-display: optimize gfx late resume code for DVx

gfx-display: optimize gfx late resume code for DVx

BZ: 33421

remove redundant code in mipi encoder mode set, and make some optimiaztions to make
gfx late resume faster for DVx. with this patch, time consumption of gfx_late_resume
is almost the same with PRx.

Change-Id: Ied6e1ade9874139bd69d8dbab1728f5516632151
Signed-off-by: Geng Xiujun <xiujun.geng@intel.com>
Reviewed-on: http://android.intel.com:8080/48654
Reviewed-by: Xu, Randy <randy.xu@intel.com>
Tested-by: Tong, BoX <box.tong@intel.com>
Tested-by: Xu, Randy <randy.xu@intel.com>
Reviewed-by: Imberton, Guilhem <guilhem.imberton@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>