Move ARM-specific ADC Driver reqs to own section

docs/adc_driver.md

@@ -18,19 +18,7 @@ Then place this include at the top of your code:
 #include "analog.h"
 ```
 
-### ARM Usage
-If using an ARM device, you will _also_ need to add the following to `mcuconf.h`:
-
-```c
-#undef STM32_ADC_USE_ADC1
-#define STM32_ADC_USE_ADC1 TRUE
-```
-
-Add the following to `halconf.h`:
-
-```c
-#define HAL_USE_ADC TRUE
-```
+If using ARM, there are additional requirements detailed in [ARM Additional Requirements](#arm-additional-requirements).
 
 ## Channels
 
@@ -157,6 +145,21 @@ Also note that the F0 and F3 use different numbering schemes. The F0 has a singl
 
 ## Configuration
 
+### ARM Additional Requirements
+
+If using an ARM device, you will need to add the following to `mcuconf.h`:
+
+```c
+#undef STM32_ADC_USE_ADC1
+#define STM32_ADC_USE_ADC1 TRUE
+```
+
+And add the following to `halconf.h`:
+
+```c
+#define HAL_USE_ADC TRUE
+```
+
 ## ARM
 
 The ARM implementation of the ADC has a few additional options that you can override in your own keyboards and keymaps to change how it operates. Please consult the corresponding `hal_adc_lld.h` in ChibiOS for your specific microcontroller for further documentation on your available options.