qcom-charger: smb138x-charger: add parallel enable status properties

qcom-charger: smb138x-charger: add parallel enable status properties

There are several ways that the parallel charger can be enabled, and
disabled. Currently charging is enabled by default, but the hardware has
the option to disable the parallel charger via the CHG_EN pin on the
parallel charger. The parallel charger driver controls when the
parallel charger is enabled via the input suspend bit.

To better understand the state of the parallel charger add two power
supply properties to the parallel power supply:

CHARGING_ENABLED	- Reflects whether the parallel charger is
			  enabled by any source.
PIN_ENABLED		- Reflects whether hardware has voted to enable
			  the parallel charger.

Change-Id: I725245178ab02c5ec39b89998f5c2ca3d494c8ee
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>