Enhance the stm32_dmacapable implementation to give correct answers.
Fix the Kconfig configuration for the STM32 SDIO DMA priority option.
Teach the STM32 SDIO driver how to determine whether a transfer can be performed safely using DMA.
Teach the MMC layer to handle errors reported during DMA setup.
Teach the FAT filesystem how to deal with I/Os that can't be handled due to DMA non-conformability.
Fix DMA channel definitions for UART7/8
Add an explicit preflight call for SDIO DMA operations, since we can't error out of the DMA setup (the card is already committed at that point).
Missed de-optioning the DMA preflight check.