libfdt: Fix NOP handling bug in fdt_add_subnode_namelen()

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> fdt_add_subnode_namelen() has a bug if asked to add a subnode to a
> node which has NOP tags interspersed with its properties.  In this
> case fdt_add_subnode_namelen() will put the new subnode before the
> first NOP tag, even if there are properties after it, which will
> result in an invalid blob.
> 
> This patch fixes the bug, and adds a testcase for it.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

Thanks,
jdl