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>

include/init.h

@@ -267,6 +267,9 @@ void bdinfo_print_num(const char *name, ulong value);
 /* Print a clock speed in MHz */
 void bdinfo_print_mhz(const char *name, unsigned long hz);
 
+/* Show arch-specific information for the 'bd' command */
+void arch_print_bdinfo(void);
+
 #endif	/* __ASSEMBLY__ */
 /* Put only stuff here that the assembler can digest */