common: board_r: Drop arch-specific ifdefs around initr_trap

In order to remove the arch-specific ifdefs around initr_trap, introduce
arch_initr_trap weak initcall. Implementations for ppc/m68k/mips have
been moved to arch/<arch>/lib/traps.c

Default implementation is a nop stub.

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

arch/powerpc/lib/Makefile

@@ -40,6 +40,7 @@ obj-y	+= interrupts.o
 obj-$(CONFIG_CMD_KGDB) += kgdb.o
 obj-y	+= stack.o
 obj-y	+= time.o
+obj-y	+= traps.o
 endif # not minimal
 
 ifdef CONFIG_SPL_BUILD

arch/powerpc/lib/traps.c

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2003
+ * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+ */
+
+#include <common.h>
+#include <init.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+void trap_init(unsigned long reloc_addr);
+
+int arch_initr_trap(void)
+{
+	trap_init(gd->relocaddr);
+
+	return 0;
+}