ti_adc108s102: fix verification off-by-one
ti_adc108s102: fix verification off-by-one

Channel IDs start at 0, need to fail if the provided ID
equals ADC108S102_CHANNELS, not just larger than it.

Signed-off-by: Andrew Boie <aab045b28152628be6af0e556050d0381fd0a34d@intel.com>

galak/zephyr,galak/zephyr,ldts/zephyr,explora26/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,mbolivar/zephyr,kraj/zephyr,punitvara/zephyr,Vudentz/zephyr,mbolivar/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,zephyriot/zephyr,zephyriot/zephyr,zephyriot/zephyr,nashif/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,explora26/zephyr,nashif/zephyr,explora26/zephyr,punitvara/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,mbolivar/zephyr,nashif/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,mbolivar/zephyr,ldts/zephyr,kraj/zephyr,zephyriot/zephyr,explora26/zephyr,mbolivar/zephyr,kraj/zephyr,nashif/zephyr,ldts/zephyr,finikorg/zephyr,Vudentz/zephyr,kraj/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr