hwmon/w83627ehf: Fix the fan5 clock divider write

Users have been complaining about the w83627ehf driver flooding their logs
with debug messages like:

w83627ehf 9191-0a10: Increasing fan 4 clock divider from 64 to 128

or:

w83627ehf 9191-0290: Increasing fan 4 clock divider from 4 to 8

The reason is that we failed to actually write the LSB of the encoded clock
divider value for that fan, causing the next read to report the same old value
again and again.

Additionally, the fan number was improperly reported, making the bug harder to
find.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>