qcacmn: Initialize wlan config structure

When RRI over DDR feature is not enabled,
the variable rri_over_ddr_cfg_valid goes uninitialzed.
This can lead to unpredictable behaviour.

Fix this by initializing pld_wlan_enable_cfg to zero
before use.

Change-Id: I485dc552201111834375411b9a493ddbf9a7505c
CRs-Fixed: 3176497