arm64: dts: ti: k3-am65-main: Add DMA entries for main_spi0

Add DMA entry for main_spi0, that has SPI flash connected, for better
throughput and reduced CPU load.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>