Consolidate cuboot initialization code

[Scott Wood]

David Gibson wrote:
> +void cuboot_init(unsigned long r4, unsigned long r5,
> +		 unsigned long r6, unsigned long r7,
> +		 unsigned long end_of_ram);
> +
> +#define CUBOOT_INIT() \
> +	do { \
> +		memcpy(&bd, (bd_t *)r3, sizeof(bd)); \
> +		cuboot_init(r4, r5, r6, r7, bd.bi_memstart + bd.bi_memsize); \
> +	} while (0)

Is there any particular reason to not just do a direct call to 
cuboot_init, and move the memcpy and end-of-ram calculation there?  I'd 
rather avoid macros if possible.

Also, the "extern char _dtb_start[], _dtb_end[];" line in cuboot.c 
doesn't appear to be needed.

Other than that, it looks good.

-Scott