HDMI-CEC: Restore full volume device condition to send cec volume keys [1/1]

Volume adjustment is done on AVR while a headphone is connected. The
current output audio device is already updated from hdmi_arc to
headphone. This patch adds full volume check for a tv device, such that
it only send cec volume keyevents when current device is a full volume device.

Test: verified by vendor
Bug: b/359078216
Flag: EXEMPT bugfix
Change-Id: Iac4f6f4bf53733ee54ceb8f2da2885b21272dcfc
Signed-off-by: an.xi <an.xi@amlogic.com>