bionic:Add new header files for graphics

The header files "hwmem.h" and "b2r2_blt.h" are needed
by the ST-Ericsson graphics implementation.

Change-Id: Ied4595c24aac140090c3feaed9fbc36e6c70f2a7
Signed-off-by: Patrik Ryd <patrik.ryd@stericsson.com>