MIPS: call debug_uart_init right before board_init_f

All MIPS boards that support debug uart are calling debug_uart_init right at
the beginning of board_early_init_f.
Instead of doing that, let's provide a generic call to debug_uart_init right
before the call to board_init_f if debug uart is enabled for boards without
stack in SRAM.
On the other hand, boards with stack in SRAM can call earlier (right before
low level init).

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

arch/mips/cpu/start.S

@@ -237,6 +237,13 @@ wr_done:
 #ifdef CONFIG_MIPS_INIT_STACK_IN_SRAM
 	/* Set up initial stack and global data */
 	setup_stack_gd
+
+# ifdef CONFIG_DEBUG_UART
+	/* Earliest point to set up debug uart */
+	PTR_LA	t9, debug_uart_init
+	jalr	t9
+	 nop
+# endif
 #endif
 
 #ifndef CONFIG_SKIP_LOWLEVEL_INIT
@@ -263,6 +270,13 @@ wr_done:
 #ifndef CONFIG_MIPS_INIT_STACK_IN_SRAM
 	/* Set up initial stack and global data */
 	setup_stack_gd
+
+# ifdef CONFIG_DEBUG_UART
+	/* Earliest point to set up debug uart */
+	PTR_LA	t9, debug_uart_init
+	jalr	t9
+	 nop
+# endif
 #endif
 
 	move	a0, zero		# a0 <-- boot_flags = 0