[MIPS] RM7000: Enable ICACHE_REFILLS_WORKAROUND_WAR.

The RM7000 processors and the E9000 cores have a bug (though PMC-Sierra
opposes it being called that) where invalid instructions in the same
I-cache line worth of instructions being fetched may case spurious
exceptions.

The workaround for this was only enabled for E9000 cores; enable it also
for all RM7000-based platforms.

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