dma: Introduce STM32F4x DMA driver

This driver currently only handles memory-to-memory transfers.

TODO: Add support for all types of transfers.

Change-Id: Ic9787dcca919a58fb11b48c9f6b6b371db88c3ea
Origin: Original
Maintained-by: Zephyr
Signed-off-by: Lee Jones <lee.jones@linaro.org>