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>
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index f61809a..2782740 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -40,6 +40,7 @@
 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