Revert "wifi: remove wifi instance name string check"

This reverts commit 1c50a59e.

Reason for revert: This was not needed. Does not fix the issue at hand.
Bug: 161951052
Test: atest VtsHalWifiSupplicantV1_1TargetTest

Change-Id: I872a1b3e87f17a43eb3c22c930e916c7e5e2d2a6