dt-bindings: add ARMv8 PMU binding

Add missing "arm,armv8-pmuv3" compatible property for ARMv8 PMU.

Change-Id: I9408cdd606761b2cf5c9fc5d67a8df7a39a21352
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Git-commit: f04bda90392b729fea9b0420b2a87aa6f2abfcd9
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Neil Leeder <nleeder@codeaurora.org>