[ Upstream commit 29f58ff06795a923407d011d4721eaf3e8d39acc ]

Implement set_bias_level to drive shutdown bit, so device is
put to sleep when unused.
Signed-off-by: NLadislav Michl <ladis@linux-mips.org>
Signed-off-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>