Ultrasound: Add digital pen background side-channel resource

Add an image resource for the digital pen service status bar
notification for background side channel.

Change-Id: Ic1f4eb8b882c5fda9af4bf8dba74f2291f11e020
Merge "Ultrasound: Add digital pen background side-channel resource"
Merge 5eb4a39feba11d3a116ea790974ba742ed81ab5c on remote branch

Change-Id: I302eba10e769cc9def553a955c603ab4078a4f20
Merge "Merge 5eb4a39feba11d3a116ea790974ba742ed81ab5c on remote branch"