boards/nrf51: remove ADC_NUMOF define when not needed

boards/calliope-mini/include/periph_conf.h

@@ -90,15 +90,6 @@ static const i2c_conf_t i2c_config[] = {
 #define I2C_NUMOF           (sizeof(i2c_config) / sizeof(i2c_config[0]))
 /** @} */
 
-/**
- * @name    ADC configuration
- *
- * The configuration consists simply of a list of channels that should be used
- * @{
- */
-#define ADC_NUMOF          (0)
-/** @} */
-
 /**
  * @name    PWM configuration
  * @{

boards/microbit/include/periph_conf.h

@@ -96,15 +96,6 @@ static const i2c_conf_t i2c_config[] = {
 #define I2C_NUMOF           (sizeof(i2c_config) / sizeof(i2c_config[0]))
 /** @} */
 
-/**
- * @name   ADC configuration
- *
- * The configuration consists simply of a list of channels that should be used
- * @{
- */
-#define ADC_NUMOF          (0)
-/** @} */
-
 #ifdef __cplusplus
 }
 #endif

boards/nrf51dongle/include/periph_conf.h

@@ -40,15 +40,6 @@ extern "C" {
 #define UART_PIN_CTS        10
 /** @} */
 
-/**
- * @name   ADC configuration
- *
- * The configuration consists simply of a list of channels that should be used
- * @{
- */
-#define ADC_NUMOF          (0)
-/** @} */
-
 #ifdef __cplusplus
 }
 #endif

boards/nrf6310/include/periph_conf.h

@@ -68,16 +68,6 @@ static const spi_conf_t spi_config[] = {
 #define SPI_NUMOF           (sizeof(spi_config) / sizeof(spi_config[0]))
 /** @} */
 
-/**
- * @name    ADC configuration
- *
- * The configuration consists simply of a list of channels that should be used
- * @{
- */
-#define ADC_NUMOF          (0)
-/** @} */
-
-
 #ifdef __cplusplus
 }
 #endif