WifiHAl:Create separate create/delete virtual iface functions

The function wifi_add_or_remove_iface was taking care for
creation and deletion of virtual Iface. Added new separate
functions that will perform create and delete operations
instead of one single API.

Bug: 153852667
Bug: 154279995
Test: Pass wifi aware tests of CtsVerifier.
CRs-Fixed: 2633140
Change-Id: I3c175b1f5a59c6d022b2db51cfc72b48582ec3cf