perf: Introduce a LLCC PMU

Some chips have hardware that can count misses for LLCC at a per-CPU level.
This PMU serves as an intermediary that allows us to retrieve these values
for use in other drivers.

Change-Id: I1dc3090a64ec7d5b12a36b0395c42930128287fe
Signed-off-by: Jonathan Avila <avilaj@codeaurora.org>