imx: add basic i.MX9 support

Add i.MX9 Kconfig and basic files for the new SoC

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/spl.c b/arch/arm/mach-imx/spl.c
index e5ad993..ef00969 100644
--- a/arch/arm/mach-imx/spl.c
+++ b/arch/arm/mach-imx/spl.c
@@ -147,7 +147,7 @@
 	return BOOT_DEVICE_NONE;
 }
 
-#elif defined(CONFIG_MX7) || defined(CONFIG_IMX8M) || defined(CONFIG_IMX8)
+#elif defined(CONFIG_MX7) || defined(CONFIG_IMX8M) || defined(CONFIG_IMX8) || defined(CONFIG_IMX9)
 /* Translate iMX7/i.MX8M boot device to the SPL boot device enumeration */
 u32 spl_boot_device(void)
 {