NOUPSTREAM: perf: arm_cmn: add new code drop off from ARM.

Update the code got from ARM with the following modification:
- Don't use snapshot. It seems not working yet.
- Implement IRQ handling.
- Improve reading and setting period counter.
- arm-cmn.c was manually replaced by the new one. There are no invidual patches.

Link to ARM repo: http://linux-arm.org/git?p=linux-rm.git;a=shortlog;h=refs/heads/cmn-pmu

NOUPSTREAM as ARM will do it.

Signed-off-by: Tuan Phan <[email protected]>