MLK-23981 arm64: imx8x-mek.dtsi: Enable adma_pwm node in display specific DT file

MLK-23981 arm64: imx8x-mek.dtsi: Enable adma_pwm node in display specific DT file

The current DT file for the i.MX8x MEK platform has a pin conflict for
IMX8QXP_SPI0_CS1 bewteen the sai1 node and the adma_pwm node(as needed
by the parallel display panel backlight control).  This patch enables
the adma_pwm node in display specific DT file to avoid the conflict.
Also, the lcdif_backlight is moved to display specific as it is
referencing the adma_pwm node.

Fixes: 62408b1461b6 ("LF-1189-13 arm64: dts: imx8qxp-mek: Add adma_pwm support")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>