hwmon: (w83627ehf) Use request_muxed_region

Serialize access to the hardware by using "request_muxed_region".
Call to this macro will hold off the requestor if the resource is
currently busy. "superio_enter" will return an error if call to
"request_muxed_region" fails.

Signed-off-by: Katsumi Sato <sato@toshiba-tops.co.jp>
Signed-off-by: Atsushi Nemoto <nemoto@toshiba-tops.co.jp>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>