ARM: defconfig: add unified config for RPi3 and RPi4

Provide a defconfig which allows us to boot Raspberrry Pi 4
and Raspberry Pi 3 Model B/B+
Instead of using the embedded DTB as done in RPi3 we use the
devicetree provided by the firmware.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/arch/arm/mach-bcm283x/Kconfig b/arch/arm/mach-bcm283x/Kconfig
index e8e0ff0..00419bf 100644
--- a/arch/arm/mach-bcm283x/Kconfig
+++ b/arch/arm/mach-bcm283x/Kconfig
@@ -188,6 +188,13 @@
 	  This option creates a build targeting the ARMv8/AArch64 ISA.
 	select BCM2711_64B
 
+config TARGET_RPI_ARM64
+	bool "Raspberry Pi one binary 64-bit build"
+	help
+	  Support for all armv8 based Raspberry Pi variants, such as
+	  the RPi 4 model B, in AArch64 (64-bit) mode.
+	select ARM64
+
 endchoice
 
 config SYS_BOARD