Documentation: remove dynamic-resolution-notes reference to non-existent file

File dt-object-internal.txt does not exist. This patch removes
a reference to it.

Signed-off-by: Harish Jenny K N <harish_kandiga@mentor.com>
Reviewed-by: Frank Rowand <frank.rowand@sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>