coresight: etm_pmu: Set the module field

struct pmu::module must be set to the module owning the PMU driver.
Set this for the coresight etm_pmu.

Fixes: 8e264c52 ("coresight: core: Allow the coresight core driver to be built as a module")
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230405094922.667834-1-suzuki.poulose@arm.com