ARM: dts: imx: update sdma node name format

[ Upstream commit 6769089e ]

Node names should be generic, so change the sdma node name format 'sdma'
into 'dma-controller'.

Acked-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Joy Zou <joy.zou@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Stable-dep-of: be18293e ("ARM: dts: imx: Set default tuning step for imx7d usdhc")
Signed-off-by: Sasha Levin <sashal@kernel.org>