drivers: perf: arm_pmuv3: Merge branch filter requests on the PMU

This merges branch sample filter requests from all events that are being
scheduled on the PMU during armpmu_start(). This also drops filter check
during PMU interrupt handling. Hence all overflown eventsi, will receive
branch records captured from a merged branch filter configuration on the
PMU.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>