boards: nxp: imx8m/n/p, imx93/5, fix ram dts node name

For Zephyr Cortex-A Core supports on NXP boards imx8mm, imx8mn, imx8mp,
imx93 and imx95, currently use DDR DRAM memory as Zephyr memory, so
change RAM dts nodes name to be "dram" in order to reduce confusion.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>