[PATCH] w83781d: Document the alarm and beep bits

Document the individual alarm and beep bits of the w83781d driver.
Ideally we would offer a chip-independant interface for them, but
until it's done, it's only fair that we document the current
interface.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>