power: qpnp-fg-gen4: Support booting without a battery

There are some requirements to boot without a battery but only
with a strong charger connected for factory testing. Add support
for this by detecting battery missing condition early in the
driver probe and handling it.

While at it, add power_supply_put() for bms psy so that the
ref count for that power supply is decremented correctly.

Change-Id: If33e300874fd0f64dee6ae98ee05ae32ba14930d
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>