Fix missing ADC4 dma mapping for F3.

Fix incorrect count of dma options for F3.

Value was hardcoded to 3, but the F3 has 4 ADCs.

Fix dmaPeripheralMapping for F3.

The dmaPeripheralMapping table was using index numbers and not device
numbers.

This meant all the dma mappings were out by one, eg.

```

```

ADC 1 is on DMA1, channel 1, but the output from dma ADC 2 list shows
the possibilities for ADC 1, not ADC 2 and shows no possibilities for
dma ADC 1 list

Ensure there are defaults for ADC4 on F3.

Always use 4 ADC instances for the ADC PG.

* PG should not be target dependant.
* Add a static assert which will fail if anything is changed.

Fix dmaopt in ADC PG, it should be a int8_t, not uint8_t

Fix occurrences of -1 that should be `DMA_OPT_UNUSED`.

Fixing this meant that dma_reqmap.h needed to be included in a few
places.  When this was done there were errors because dma_reqmap.h was
included more than once and it's `#pragma once` was commented out.

Including dma_reqmap.h from every PG that uses `dmaopt` also caused
other compilation issues, fixed by this commit.

src/main/pg/timerup.h

@@ -23,6 +23,7 @@
 #include "pg/pg.h"
 #include "pg/pg_ids.h"
 
+#include "drivers/dma_reqmap.h"
 #include "drivers/io.h"
 #include "drivers/timer.h" // For HARDWARE_TIMER_DEFINITION_COUNT