HDMICEC: Correct Mute Key Press

Change to KEYCODE_VOLUME_MUTE from KEYCODE_MUTE.

Test: atest HdmiCecSystemAudioControlTest#cect_11_2_15_12_MuteUserControlPressed
Bug: 151594153
Change-Id: Ie7b0bb2f934b01fdfede0ffaaea0202dea97379c
Merged-In: Ie7b0bb2f934b01fdfede0ffaaea0202dea97379c
1 file changed