perf: qcom: Add L3 cache PMU driver

This adds a new dynamic PMU to the Perf Events framework to program
and control the L3 cache PMUs in some Qualcomm Technologies SOCs.

The driver supports a distributed cache architecture where the overall
cache for a socket is comprised of multiple slices each with its own PMU.
Access to each individual PMU is provided even though all CPUs share all
the slices. User space needs to aggregate to individual counts to provide
a global picture.

The driver exports formatting and event information to sysfs so it can
be used by the perf user space tools with the syntaxes:
   perf stat -a -e l3cache_0_0/read-miss/
   perf stat -a -e l3cache_0_0/event=0x21/

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Agustin Vega-Frias <agustinv@codeaurora.org>
[will: fixed sparse issues]
Signed-off-by: Will Deacon <will.deacon@arm.com>