Lenovo H8: Fix h8_set_audio_mute()

Lenovo H8: Fix h8_set_audio_mute()

Logic is inverted (if argument is true, one would expect that
mute is enabled) and the wrong bit was used (1 instead 0)

Change-Id: I71133ba639f1fb0d3c3582f16211dd266a11cc64
Signed-off-by: Sven Schnelle <svens@stackframe.org>
Reviewed-on: http://review.coreboot.org/334
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>