arm64: dts: imx: Add imx8mm-prt8mm.dtb to build

imx8mm-prt8mm.dts was not getting built. Add it to the build.

Fixes: 58497d7a ("arm64: dts: imx: add Protonic PRT8MM board")
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/Makefile

@@ -66,6 +66,7 @@ dtb-$(CONFIG_ARCH_MXC) += imx8mm-mx8menlo.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mm-nitrogen-r2.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mm-phg.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mm-phyboard-polis-rdk.dtb
+dtb-$(CONFIG_ARCH_MXC) += imx8mm-prt8mm.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mm-tqma8mqml-mba8mx.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mm-var-som-symphony.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mm-venice-gw71xx-0x.dtb