of: base: improve of_get_next_child() kernel-doc
of: base: improve of_get_next_child() kernel-doc

Add two new facts to of_get_next_child() documentation:

   * of_get_next_child() returns NULL when there is not next child

   * of_get_next_child() decrements the refcount of prev

Signed-off-by: Baruch Siach <53ccad33e0625915318fb3bc832e5c1c413d1294@tkos.co.il>
Signed-off-by: Rob Herring <fbb37eacae100e13076d5c4b46f06cfa4d6fa9f8@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs