power: qpnp-fg-gen4: schedule pl_current_en_work conditionally

Currently, pl_current_en_work is scheduled whenever the status
change work runs which is based on the notifications from other
power supplies. Also, it is made to run 1 second after enabling
mem_attn interrupt if it is disabled. This is to ensure that
parallel current summing configuration is made at the right
instant as per the hardware recommendation. If a work is pending
already mostly scheduling after enabling mem_attn interrupt, do
not schedule another work. This way, a possible race condition
can be avoided when changing parallel current summing
configuration.

Also, schedule the work only if parallel charger is available as
it is not required when charge pump is paired with the main
charger.

Change-Id: I66b767b26a2876884ba0d4b015311bd4dd090a3e
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>