hwmon: (w83627ehf) don't assume bank 0

Don't assume that the default bank is 0. For one thing, we don't even
set it to 0 when the driver is loaded, so the initial state might be
different. For another, something (say, the BIOS) might access the chip
and leave with the bank set to something different, so assuming that
the bank value is 0 is not safe.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>