power: qpnp-smbcharger: Check for parallel-charger's presence

The parallel charging configuration is being applied without
checking if a parallel-charger is actually present. Fix
this by checking its presence before configuring it.

CRs-Fixed: 846331
Change-Id: Iffd1c22922c75bd4ea3feaabf33f727df852c984
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>