MIPS: Allow pre-r6 emulation on SMP MIPSr6 kernels

MIPS: Allow pre-r6 emulation on SMP MIPSr6 kernels

There's no reason for the pre-r6 instruction emulation code to be
limited to uniprocessor kernels. We already emulate atomic memory access
instructions in a way that works for SMP systems, and nothing else
should be affected. Remove the artificial limitation, allowing pre-r6
instruction emulation to be used with SMP kernels.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14410/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>