refactor(rpi): split out console registration logic

Detection of the UART in use and GPIO code only apply to RPi 3 and 4.

RPi 5 has a dedicated PL011 debug port.

Change-Id: Iddf8aea01278e2b79b4e7c476740f1add8c419f0
Signed-off-by: Mario Bălănică <mariobalanica02@gmail.com>
diff --git a/plat/rpi/common/include/rpi_shared.h b/plat/rpi/common/include/rpi_shared.h
index 1b6c426..8562c3d 100644
--- a/plat/rpi/common/include/rpi_shared.h
+++ b/plat/rpi/common/include/rpi_shared.h
@@ -7,14 +7,20 @@
 #ifndef RPI_SHARED_H
 #define RPI_SHARED_H
 
+#include <stddef.h>
 #include <stdint.h>
 
+#include <drivers/console.h>
+
 /*******************************************************************************
  * Function and variable prototypes
  ******************************************************************************/
 
-/* Utility functions */
+/* Serial console functions */
 void rpi3_console_init(void);
+int rpi3_register_used_uart(console_t *console);
+
+/* Utility functions */
 void rpi3_setup_page_tables(uintptr_t total_base, size_t total_size,
 			    uintptr_t code_start, uintptr_t code_limit,
 			    uintptr_t rodata_start, uintptr_t rodata_limit