MIPS: Add set/clear CP0 macros for PageGrain register

Build set and clear macros for the PageGrain register.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9289/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --cc arch/mips/include/asm/mipsregs.h
Simple merge

diff --cc arch/mips/kernel/cpu-probe.c
Simple merge

diff --cc arch/mips/mm/tlb-r4k.c
Simple merge