power: smb1381: fix NULL pointer dereference

In standalone mode "parallel_psy" is not valid, add check
to validate parallel_psy before dereferencing.

Change-Id: I902ff2488a662c1994af88565f74d5dc7b8c3e4e
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>