arm64: dts: fsl: DPAA FMan DMA operations are coherent

Although the DPAA 1 FMan operations are coherent, the device tree
node for the FMan does not indicate that, resulting in a needless
loss of performance. Adding the missing dma-coherent property.

Fixes: 1ffbecdd ("arm64: dts: add DPAA FMan nodes")
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Tested-by: Camelia Groza <camelia.groza@oss.nxp.com>
Acked-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>