hwspinlock/msm: Add support for Qualcomm MSM HW Mutex block

Add driver for Qualcomm MSM Hardware Mutex block that exists on
newer Qualcomm SoCs.

Cc: Jeffrey Hugo <jhugo@codeaurora.org>
Cc: Eric Holmberg <eholmber@codeaurora.org>
Cc: Courtney Cavin <courtney.cavin@sonymobile.com>
Signed-off-by: Kumar Gala <galak@codeaurora.org>
[bjorn: added pm_runtime calls, from Courtney,
	added sfpb-mutex compatible,
	updated DT binding documentation formatting]
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>