rhine-common: Omni-fy
rhine-common: Add ril_msim.h

Omni doesn't have mSIM support in the framework yet, but Sony Qualcomm devices run their own
libril which depends on the header. Add it to satisfy build requirements until mSIM support
can be properly integrated into Omni.
rhine-common: Comment out TW_BOARD_CUSTOM_GRAPHICS

The file is outdated and obsolete, using graphics.c from mainline TWRP should be just fine.