Use the DEVICE_ATTR_(RO|RW) macros, ranaming the show and store
functions accordingly.
Signed-off-by: NDarren Hart (VMware) <dvhart@infradead.org>
Tested-by: NCarlo Caione <carlo@endlessm.com>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>