ARM: dts: Disable DMA support on the BK4 vf610 device's fsl_lpuart

This change disables the DMA support (RX/TX) on the NXP's fsl_lpuart
driver - the PIO mode is used instead. This change is necessary for better
robustness of BK4's device use cases with many potentially interrupted
short serial transfers.

Without it the driver hangs when some distortion happens on UART lines.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>