MIPS: Fix regression on BCM4710 processor detection

BCM4710 uses the BMIPS32 core (like BCM6345), not the MIPS 4Kc core as
was previously believed.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Tested-by: Alexandros C. Couloumbis <alex@ozo.com>
Patchwork: https://patchwork.linux-mips.org/patch/1837/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>