hwmon: (da9052) Synchronize access with mfd

[ Upstream commit 333e22db228f0bd0c839553015a6a8d3db4ba569 ]

When tsi-as-adc is configured it is possible for in7[0123]_input read to
return an incorrect value if a concurrent read to in[456]_input is
performed. This is caused by a concurrent manipulation of the mux
channel without proper locking as hwmon and mfd use different locks for
synchronization.

Switch hwmon to use the same lock as mfd when accessing the TSI channel.

Fixes: 4f16cab1 ("hwmon: da9052: Add support for TSI channel")
Signed-off-by: Samu Nuutamo <samu.nuutamo@vincit.fi>
[rebase to current master, reword commit message slightly]
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>