arm64: dts: imx8-ss-audio: remove memory-region = <&dsp_reserved>;

Different boards have different DDR memory sizes and layouts for reserved
memory. This change reduces future dependencies to add 'imx8qm-ss-audio'.
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8-ss-audio.dtsi

@@ -447,7 +447,6 @@ dsp: dsp@596e8000 {
 			<&lsio_mu13 2 1>,
 			<&lsio_mu13 3 0>,
 			<&lsio_mu13 3 1>;
-		memory-region = <&dsp_reserved>;
 		status = "disabled";
 	};