wifi(implementation): Stop loading vendor library statically

libwifi-hal statically imports the vendor implementation of the legacy
HAL. Since the HIDL daemon is dynamically linking against libwif-hal,
there is no need for it to statically import the vendor implementation
library (one pointed to by: $LIBWIFI-HAL variable).

Bug: 36169790
Test: Compiles & device is able to connect to wifi networks with the
change.

Change-Id: Ie44b58328f9bdde011ba6d4a4d26f786c2d097e7