[PULL] perf support for X-Gene

[Dann Frazier]

This branch makes perf work on X-Gene:

git://kernel.ubuntu.com/dannf/ubuntu-utopic-hyperscale.git xgene-perf

A working perf tool is expected by users these days, and it's absence
makes it a real pain to do any performance triage with the official
Ubuntu kernel builds.

There are 2 pieces here - the device-tree binding/node and a bug fix.

The device-tree node has been submitted twice upstream (initially back
in March and again earlier this month), but hasn't gotten a response
from upstream yet. It is obviously correct IMO. The only thing I could
possibly see changing upstream would be to select a compatible string
other than "potenza-pmu". But that wouldn't be a problem for Ubuntu as
no existing driver code binds to it.

The other patch in this series is the "irqchip:gic: change access of
gicc_ctrl register to read modify write." patch. This patch fixes a
crash that is very easy to reproduce by running "perf top". We've been
testing with this patch for some time now with no negative results.
This patch was submitted a few times, but the last submission in
February never saw any upstream feedback. Now that the upstream gic
code has been reworked to support GICv3 (post-3.16), this code will
need to be reworked to apply for mainline.