libfdt: Remove no longer used code from fdt_node_offset_by_compatible()

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> Since fdt_node_offset_by_compatible() was converted to the new
> fdt_next_node() iterator, a chunk of initialization code became
> redundant, but was not removed by oversight.  This patch cleans it up.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

jdl