iio: accel: sca3300: add define for temp channel for reuse.

Add define of SCA3300_TEMP_CHANNEL for reuse.

Signed-off-by: LI Qingwu <Qing-wu.Li@leica-geosystems.com.cn>
Reviewed-by: Tomas Melin <tomas.melin@vaisala.com>
Link: https://lore.kernel.org/r/20220529061853.3044893-3-Qing-wu.Li@leica-geosystems.com.cn


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>