bdinfo: arm: Move ARM-specific info into its own file

We don't really want to have ARM-specific code in a generic file. Create
a new arch-specific function to hold it, and move it into that.

Make the function weak so that any arch can implement it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index b839aa7..27b12e7 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -43,6 +43,7 @@
 obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMCPY) += memcpy.o
 obj-$(CONFIG_SEMIHOSTING) += semihosting.o
 
+obj-y	+= bdinfo.o
 obj-y	+= sections.o
 obj-y	+= stack.o
 ifdef CONFIG_CPU_V7M