Added indication update mode support

Adde the indication update mode support so that a system
component can control the behavior of indication update. This
will be used by the bluetooth stack when some BT devices such like
carkit is connected, modem will continue update the signal strength
even when the screen is off.

Test: Manual
Bug: 65112388
Change-Id: I725002afd47e14682cf2ffa669f0686167e13802