boards: mimxrtXXX: Add UART DMAs

Add DMA phandles to UART nodes in RT 3 digit EVK
dts files now that the UART ASYNC API is supported
in the mcux flexcomm driver.

Also add the DMA phandles to other platforms with
flexcomm uart and lpc dma enabled by default for
compatibility

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>
4 files changed