wifidisplay: restrict broadcast by the proper permission

WIFI_DISPLAY_STATUS_CHANGED event contains the MAC address of peers.
As the MAC address is PII data, this should be restricted by proper
permission.

Bug: 176541017
Test: install PoC in b/176541017 and check PII data is not leaked.
Change-Id: I36b85f44678fe232486702fa009f5f06d1a7af75