spmi: pmic_arb: add support for hw version 2

Qualcomm PMIC Arbiter version-2 changes from version-1 are:

- Some different register offsets.
- New channel register space, one per PMIC peripheral (ppid).
  All tx traffic uses these channels.
- New observer register space. All rx trafic uses this space.
- Different command format for spmi command registers.
Reviewed-by: Sagar Dharia <sdharia@codeaurora.org>
Signed-off-by: Gilad Avidov <gavidov@codeaurora.org>
Tested-by: Ivan T. Ivanov <iivanov@mm-sol.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/spmi/qcom,spmi-pmic-arb.txt

 Qualcomm SPMI Controller (PMIC Arbiter)
 
-The SPMI PMIC Arbiter is found on the Snapdragon 800 Series.  It is an SPMI
+The SPMI PMIC Arbiter is found on Snapdragon chipsets.  It is an SPMI
 controller with wrapping arbitration logic to allow for multiple on-chip
 devices to control a single SPMI master.
 
@@ -19,6 +19,10 @@ Required properties:
      "core" - core registers
      "intr" - interrupt controller registers
      "cnfg" - configuration registers
+   Registers used only for V2 PMIC Arbiter:
+     "chnls"  - tx-channel per virtual slave registers.
+     "obsrvr" - rx-channel (called observer) per virtual slave registers.
+
 - reg : address + size pairs describing the PMIC arb register sets; order must
         correspond with the order of entries in reg-names
 - #address-cells : must be set to 2