rpi3: Rename RPI3_IO_BASE to RPI_IO_BASE

The location of the MMIO window is different between a Raspberry Pi 3
and 4: the former has it just below 1GB, the latter below 4GB.
The relative location of the peripherals is mostly compatible though.

To allow sharing code between the two models, let's rename the symbol
used for the MMIO base to the more generic RPI_IO_BASE name.

Change-Id: I3c2762fb30fd56cca743348e79d72ef8c60ddb03
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/plat/rpi/rpi3/include/platform_def.h b/plat/rpi/rpi3/include/platform_def.h
index 2a12fe7..e308f70 100644
--- a/plat/rpi/rpi3/include/platform_def.h
+++ b/plat/rpi/rpi3/include/platform_def.h
@@ -110,8 +110,8 @@
 /*
  * I/O registers.
  */
-#define DEVICE0_BASE			RPI3_IO_BASE
-#define DEVICE0_SIZE			RPI3_IO_SIZE
+#define DEVICE0_BASE			RPI_IO_BASE
+#define DEVICE0_SIZE			RPI_IO_SIZE
 
 /*
  * Arm TF lives in SRAM, partition it here