stm32: add DMA support to libuart #1596

Job	Run time
call-ci / build (armv7a7-imx6ull-evk)	1m 56s
call-ci / build (armv7a9-zynq7000-qemu)	2m 0s
call-ci / build (armv7a9-zynq7000-zedboard)	1m 18s
call-ci / build (armv7a9-zynq7000-zturn)	1m 40s
call-ci / build (armv7m4-stm32l4x6-nucleo)	1m 22s
call-ci / build (armv7m7-imxrt106x-evk)	1m 51s
call-ci / build (armv7m7-imxrt117x-evk)	1m 49s
call-ci / build (host-generic-pc)	1m 6s
call-ci / build (ia32-generic-pc)	1m 19s
call-ci / build (ia32-generic-qemu)	1m 22s
call-ci / build (riscv64-generic-qemu)	1m 14s
call-ci / build (riscv64-generic-spike)	1m 14s
call-ci / run tests on emulators (armv7a9-zynq7000-qemu)	6m 24s
call-ci / run tests on emulators (host-generic-pc)	1m 21s
call-ci / run tests on emulators (ia32-generic-qemu)	4m 47s
call-ci / run tests on hardware (armv7a7-imx6ull-evk)	3m 44s
call-ci / run tests on hardware (armv7m7-imxrt106x-evk)	1m 56s
call-ci / run tests on hardware (armv7m7-imxrt117x-evk)	2m 7s
call-ci / run tests on hardware (armv7a9-zynq7000-zedboard)	4m 48s
call-ci / run tests on hardware (armv7m4-stm32l4x6-nucleo)	9m 1s
call-ci / notify ci team using e-mail	0s
	52m 19s

Provide feedback