[TNU1.2] Add string for client number notification

Add string for client number notification

Bug: 122085773
Test: atest TetheringTests
Change-Id: Icc4e59ce3b2d8d4c1c7883c2f9d040d3ce563f09
Merged-In: Icc4e59ce3b2d8d4c1c7883c2f9d040d3ce563f09
(cherry picked from aosp/1259995)
4 files changed