arm64: dts: imx95: Correct the lpuart7 and lpuart8 srcid

According to the imx95 RM, the lpuart7 rx and tx DMA's srcid are 88 and 87,
and the lpuart8 rx and tx DMA's srcid are 90 and 89. So correct them.

Fixes: 915fd2e1 ("arm64: dts: imx95: add edma[1..3] nodes")
Signed-off-by: Joy Zou <joy.zou@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>