The macro was moved from Kconfig to the periph_cpu.h which means that
the macro name needed to be updated to BOARD_HAS_ADC_PA06_CAP instead
of CONFIG_BOARD_HAS_ADC_PA06_CAP.
The ADC in the QN908x cpu offers multiple options for ADC conversion
using up to 8 external pins, one external reference pin and some
internal signals like a 1.2V reference, Vss, Vcc and an internal
temperature monitor.
This patch implements support for sampling ADC values from the ADC lines
defined in the board configuration. Some configurations are really
always present and don't require a board configuration, like the Vcc or
internal temperature monitor but to coexist with other board ADC line
options they are only set as part of the board configuration.
