board: freescale: common: Add flag for LBMAP brdcfg reg offset

Add QIXIS_LBMAP_BRDCFG_REG to the save offset of LBMAP
configuration register instead of hardcoding it in
set_lbmap() function.

Signed-off-by: Calvin Johnson <calvin.johnson@nxp.com>
Signed-off-by: Abhimanyu Saini <abhimanyu.saini@nxp.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>