Add proper locking for the cached variables. Also get rid of
ref_is_vdd, which became obsolete.
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NJean Delvare <khali@linux-fr.org>

Add basic support for the ADT7411. Reads out all conversion results (via I2C,
SPI yet missing) and allows some on-the-fly configuration. Tested with a
custom board.
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NJean Delvare <khali@linux-fr.org>