rtc: rtc-hid-sensor-time: allow full years (16bit) in HID reports

The draft for HID-sensors (HUTRR39) currently doesn't define the range
for the attribute year.  Asking one of the authors revealed that full
years (e.g.  2013 instead of just 13) were meant.

So we now allow both, 8 bit and 16 bit values for the attribute year and
assuming full years when the value is 16 bits wide.

We will still support 8 bit values until the specification gets final
(and maybe defines a way to set the time too).

Signed-off-by: Alexander Holler <holler@ahsoftware.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>