MIPS: clear execution hazard after changing FTLB enable

On current P-series cores from Imagination the FTLB can be enabled or
disabled via a bit in the Config6 register, and an execution hazard is
created by changing the value of bit. The ftlb_disable function already
cleared that hazard but that does no good for other callers. Clear the
hazard in the set_ftlb_enable function that creates it, and only for the
cores where it applies.

This has the effect of reverting c982c6d6 ("MIPS: cpu-probe: Remove
cp0 hazard barrier when enabling the FTLB") which was incorrect.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: c982c6d6 ("MIPS: cpu-probe: Remove cp0 hazard barrier when enabling the FTLB")
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14023/


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