drivers: adc: fix license
drivers: adc: fix license

This is a leftover license header from when we used a third party
driver that had since been replaced.

Signed-off-by: Anas Nashif <0d9952ec84ac43c159f6b7e7ed99a9080c00dd6e@intel.com>

finikorg/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,Vudentz/zephyr,ldts/zephyr,ldts/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr