MIPS: Handle OCTEON BBIT instructions in FPU emulator.

The branch emulation needs to handle the OCTEON BBIT instructions,
otherwise we get SIGILL instead of emulation.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5726/


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