ASoC: WM8995: Fix incorrect use of snd_soc_update_bits()

In the wm8995_set_tristate() function when updating the register
bits use the value and not the register index as the value argument.

Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@kernel.org