Convert the mute LED handling in Realtek codec to the new vmaster mute
helper.  A point to be cautiously handled is that the value passed to
the callback is inverted; the vmaster passes "enabled" (0 = mute),
while LED classdev passes "brightness" (1 = mute).

The code in Thinkpad helper is also converted.   In that case, just
call the new function and remove the open-code.
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Link: https://lore.kernel.org/r/20200618110842.27238-10-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>