Enhanced permission checks for TelephonyManager#endCall() API.

The existing permission checks require CALL permission in order to end
an ongoing call or reject an incoming call.  The Telecom equivalent of
this API requires MODIFY_PHONE_STATE.  Since this API IS in fact a system
API, modifying the permission requirements to require the same

Test: Manual testing per bug reproduction steps.
Bug: 67862398
Change-Id: I8f15f6afd00466f6b861079a83e9fa03b962f63f
(cherry picked from commit 6707357c6e198287046e76c1d6fc5edf1fcb3fee)
(cherry picked from commit ee1901e859ed4624723d18497b70c59b0b658747)
1 file changed