net: qrtr: Use xa_load in qrtr_get_service_id

In qrtr_get_service_id, use xa_load instead of node_get to check
if the node exists or not. Calling node_get from interrupt context
can cause potential deadlock since it calls into xa_store to
allocate the node if it does not exist.

Change-Id: Ida9f7a113417f0d184c0903004d94dd2eca6c472
Signed-off-by: Sarannya S <quic_sarannya@quicinc.com>