hwmon: (adt7475) Fix masking of hysteresis registers

The wrong bits are masked in the hysteresis register; indices 0 and 2
should zero bits [7:4] and preserve bits [3:0], and index 1 should zero
bits [3:0] and preserve bits [7:4].

Fixes: 1c301fc5

 ("hwmon: Add a driver for the ADT7475 hardware monitoring chip")
Signed-off-by: Tony O'Brien <tony.obrien@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20230222005228.158661-3-tony.obrien@alliedtelesis.co.nz
Signed-off-by: Guenter Roeck <linux@roeck-us.net>