hwspinlock: qcom: Add support for Qualcomm HW Mutex block

Add driver for Qualcomm 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,
	replaced msm prefix with qcom,
	cleaned up includes]
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>