EmbeddedPkg: delete outdated FdtLib README.txt

EmbeddedPkg: delete outdated FdtLib README.txt

While looking at encoding and line ending errors, I found this file
in fact simply points to a sourceforge page which no longer exists.
Since there is nothing more to say than "this is an import of
libfdt", let's just delete it.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>