arm64: dts: freescale: rename imx93.dtsi to imx91_93_common.dtsi and modify them

The design of i.MX91 platform is very similar to i.MX93 and only
some small differences.

If the imx91.dtsi include the imx93.dtsi, each add to imx93.dtsi
requires an remove in imx91.dtsi for this unique to i.MX93, e.g. NPU.
The i.MX91 isn't the i.MX93 subset, if the imx93.dtsi include the
imx91.dtsi, the same problem will occur.

Common + delta is better than common - delta, so add imx91_93_common.dtsi
for i.MX91 and i.MX93, then the imx93.dtsi and imx91.dtsi will include the
imx91_93_common.dtsi.

Rename imx93.dtsi to imx91_93_common.dtsi and move i.MX93 specific
part from imx91_93_common.dtsi to imx93.dtsi.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Joy Zou <joy.zou@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>