MIPS: Fix MSA assembly warnings

MIPS: Fix MSA assembly warnings

Building an MSA capable kernel with a toolchain that supports MSA
produces warnings such as this:

arch/mips/kernel/r4k_fpu.S:229: Warning: the `msa' extension requires 64-bit FPRs

This is due to ".set msa" without ".set fp=64" in the non doubleword MSA
load/store macros, since MSA requires the 64-bit FPU registers (FR=1).
Add the missing fp=64 in these macros to silence the warnings.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13063/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>