iio: temperature: ltc2983: Fix macro parenthesization and rename

iio: temperature: ltc2983: Fix macro parenthesization and rename

Wrap the 'chan' parameter in LTC2983_CHAN_START_ADDR() and
LTC2983_CHAN_RES_ADDR() with parentheses to prevent potential
macro argument expansion issues. Also rename LTC2983_CHAN_START_ADDR
to LTC2983_CHAN_ASSIGN_ADDR and LTC2983_CHAN_RES_ADDR to
LTC2983_RESULT_ADDR, to better reflect the datasheet names and avoid
them being confused as related.

Reviewed-by: Joshua Crofts <joshua.crofts1@gmail.com>
Signed-off-by: Liviu Stan <liviu.stan@analog.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>