arm64: Fix show_unhandled_signal_ratelimited usage

arm64: Fix show_unhandled_signal_ratelimited usage

Commit 86dca36e6ba introduced ratelimited usage for
'unhandled_signal' messages.
The commit checks the ratelimit irrespective of whether
the signal is handled or not, which is wrong and leads
to false reports like the below in dmesg :

__do_user_fault: 127 callbacks suppressed

Do the ratelimit check only if the signal is unhandled.

Fixes: 86dca36e6ba0 ("arm64: use private ratelimit state along with show_unhandled_signals")
Cc: Vladimir Murzin <[email protected]>
Signed-off-by: Suzuki K. Poulose <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>