SurfaceFlinger: Removal of NO_RGBX_8888 flag for OMAP3

Removing this will allow color format of surface to be set for RGBX8888
that can improve performance for 32 bit framebuffer.

Tested on Nook Color with CM10
TI's commit can be found here:
review.omapzoom.org/#/c/21374/3

This will also remove the need to have BOARD_NO_RGBX_8888 := true
in the BoardConfig.mk

Change-Id: Ibc6e56c992a6433bc8688d88471d4feb9084278c