st-hal: Fix potential NULL pointer dereference

In function update_hw_config_on_start, pointer
conf_levels could be used without allocating
memory or assigning valid address. This could
cause a potential NULL pointer dereference.
Check conf_levels against NULL before using it.

Change-Id: I2bd3257a7dddaaa2ac2ca869b269c069ff655af3
1 file changed