Perf: Add API to check for PMU constraints

Extend ARM perf to check if PMU's have any special
constraints for adding events.

e.g. MSM PMU's have column exclusion constraints
that restrict adding events from the same register
and same group.

Change-Id: I36ea093c523f90f083d66dc6995e66cd77129bbd
Signed-off-by: Ashwin Chaugule <ashwinc@codeaurora.org>