arm-ccn: perf: Prevent module unload while PMU is in use

When the PMU driver is built as a module, the perf expects the
pmu->module to be valid, so that the driver is prevented from
being unloaded while it is in use. Fix the CCN pmu driver to
fill in this field.

Fixes: a33b0daa

 ("bus: ARM CCN PMU driver")
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>