Use FLAG_IMMUTABLE for MultiSimSettingController

Require that the PendingIntent be immutable so that a malicious app is
 not able to hijack and mutate any of the details.

Test: Android builds
Bug: 155094269
Change-Id: Ic7ee67a393b72121071a39f80b02538c758792c6
Merged-In: Ic7ee67a393b72121071a39f80b02538c758792c6
1 file changed