arm64: defconfig: include the Agilex platform to the arm64 defconfig

Build the Agilex platform in the standard arm64 defconfig.
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

arch/arm64/configs/defconfig

@@ -29,6 +29,7 @@ CONFIG_BLK_DEV_INITRD=y
 CONFIG_KALLSYMS_ALL=y
 # CONFIG_COMPAT_BRK is not set
 CONFIG_PROFILING=y
+CONFIG_ARCH_AGILEX=y
 CONFIG_ARCH_SUNXI=y
 CONFIG_ARCH_ALPINE=y
 CONFIG_ARCH_BCM2835=y