hwmon: (sch5627) Disallow write access if virtual registers are locked

hwmon: (sch5627) Disallow write access if virtual registers are locked

When the lock bit inside SCH5627_REG_CTRL is set, then the virtual
registers become read-only until the next power cycle.
Disallow write access to those registers in such a case.

Tested on a Fujitsu Esprimo P720.

Fixes: aa9f833dfc12 ("hwmon: (sch5627) Add pwmX_auto_channels_temp support")
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20230907052639.16491-3-W_Armin@gmx.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>