MIPS,bpf: fix missing break in switch statement

There is a missing break causing a fall-through and setting
ctx.use_bbit_insns to the wrong value. Fix this by adding the
missing break.

Detected with cppcheck:
"Variable 'ctx.use_bbit_insns' is reassigned a value before the old
one has been used. 'break;' missing?"

Fixes: 8d8d18c3

 ("MIPS,bpf: Fix using smp_processor_id() in preemptible splat.")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: David Daney <david.daney@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>