Perf: arm64: Add Snapshot of perf tracepoints

Snapshot of perf tracepoint framework taken straight of msm-4.4
commit <fec225ae458291> (Merge "qpnp-fg-gen3: prime CC_SOC_SW when
capacity learning begins")
[Fixing coding style issues]
[Switch perf_trace_counters.c to new hotplug notifier method]
[Replace inline assembly with read/write_sysreg()]
[Change perf_trace_user.h to display 7 counters like
perf_trace_counters.h]
[Change perf_trace_user.c to use debugfs_create_dir() instead
of obsolete perf_create_debug_dir()]

It contains the following squashed commit:

Perf: arm64: avoid use of uninitialized variable

Variable "buf" is not initialized. It may contain the data from
stack when "count == 0". Kernel information leak is possible due
to different code path execution.

The commit also includes the squashed patch from Olav as follows:

Perf: arm64: Use proper API to get task cpu

Instead of directly accessing thread_info structure to get the
task cpu use the appropriate wrapper API. This is needed for
subsequent patches refactors the location of task cpu.

Change-Id: I83c3ca3fbc9237c9109735f5fb2398cb4e9f6de9
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Patrick Fay <pfay@codeaurora.org>
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>