power: qpnp-fg: Fix NULL pointer dereference in battery profile init

During battery profile init 'of_batterydata_get_best_profile' can
return either an error code or NULL, handle both of these.

CRs-Fixed: 1029493
Change-Id: If98613b018e0bde6c60d374fd61487a6016c1db1
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>