msm: mhi_dev: Avoiding null pointer dereference in uci layer

Avoiding null pointer dereference in mhi_uci_client_open API in uci layer
by changing the location of the condition check for uci_handle.

Change-Id: If2cc99f47f4c5d05d0df4a5b4900894683f7c8d1
Signed-off-by: Sai Chaitanya Kaveti <quic_skaveti@quicinc.com>