rpi5: Use devicetree as alternative way to read IO base addresses

MBOX and Watchdog on RPi5/bcm2712 have a different base IO offsets.
Find them via devicetree blob passed by bootloader.

Signed-off-by: Dmitry Malkin <dmitry@bedrocksystems.com>
Reviewed-by: Matthias Brugger <mbrugger@suse.com>
Tested-by: Jens Maus <mail@jens-maus.de>
Tested-by: Darko Alavanja <darko.alavanja@konsulko.com>
Signed-off-by: Ivan T. Ivanov <iivanov@suse.de>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/arch/arm/mach-bcm283x/include/mach/mbox.h b/arch/arm/mach-bcm283x/include/mach/mbox.h
index 490664f..35d4e2f 100644
--- a/arch/arm/mach-bcm283x/include/mach/mbox.h
+++ b/arch/arm/mach-bcm283x/include/mach/mbox.h
@@ -38,8 +38,7 @@
 
 /* Raw mailbox HW */
 
-#define BCM2835_MBOX_PHYSADDR ({ BUG_ON(!rpi_bcm283x_base); \
-				 rpi_bcm283x_base + 0x0000b880; })
+#define BCM2835_MBOX_PHYSADDR	rpi_mbox_base
 
 struct bcm2835_mbox_regs {
 	u32 read;