According to 'MIPS32® interAptivTM Multiprocessing
System Programmer’s Guide' CPC_BASE_ADDR takes bits [31:15].

This change is tested ith mt7621 which wasn't working without it.
Signed-off-by: NNikolay Martynov <mar.kolya@gmail.com>
Reviewed-by: NJames Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11766/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>