libfdt: Fix use of uninitialized variable in fdt_get_path()

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> My recent implemenetation of fdt_get_path() had a bug - the while loop
> tested offset which was unitialized on the first iteration.  Depending
> on code surrounding the call, this could cause fdt_get_path() to
> return incorrect results.
> 
> This patch corrects the problem by applying some more correct thinking
> to the loop condition.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

Thanks,
jdl