ALSA: usb-audio: Add a quirk for Plantronics Gamecom 780
Plantronics Gamecom 780 headset has a firmware problem, and when the
FU 0x09 volume is changed, it results in either too loud or silence
except for a very narrow range. This patch provides a workaround,
ignoring the node, initialize the volume in a sane value and keep
untouched.