Prepares libwifi-hal for use by a vendor APEX

Creates a cc_defaults with soong config vars for libwifi-hal that
customized implementations can override.

Bug: 205065320
Test: m -j with mac80211_hwsim vendor APEX on Cuttlefish
Test: Connect to wifi
Change-Id: If7e230dfe40ef9de1e45972cbce667975c154edf
Merged-In: If7e230dfe40ef9de1e45972cbce667975c154edf
1 file changed