Bit 0, 5, and 6 in the status register are reserved and, if set, do not
indicate an alarm. Bit 7 is the 'busy' bit and also does not indicate
an alarm. Mask the non-alarm bits to avoid reporting them to userspace.

Cc: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>