arm-cci: pmu: Fix typo in event name

For one of the CCI events exposed under sysfs, "snoop" was typo'd as
"snopp". Correct this such that users see the expected event name when
enumerating events via sysfs.

Cc: arm@kernel.org
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>