Revert "f4 internal_adc driver: added .available and .number_of_channels"

This reverts commit 9d6917a3d57d464cf121de87608a3b7d1dfbc132.

Conflicts:
	flight/PiOS/STM32F4xx/pios_internal_adc.c
f4 internal_adc driver: added .available and .number_of_channels