argp-standalone: replace with a maintained fork

Remove two patches as issues fixed upstream,
submit the third one.

License-Update: argp.h is an import from glibc and
has been refreshed to the latest version. It's still
lgpl 2.1.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>