power: smb1351: Ignore ICL update if parallel slave is enabled

After the ICL split across the master and slave charger is complete,
there is a possibility of the main charger's ICL to be updated to its
total ICL value. This can lead to excessive draw from the adapter.
Avoid it by skipping this ICL update of the main charger if the
parallel slave is already enabled and configured.

CRs-Fixed: 1043224
Change-Id: I0a8c2646f1d6053e03f9ac310106ad5682bd22db
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>