MAINTAINERS: add git tree for random.c

commit 9bafaa93

 upstream.

This is handy not just for humans, but also so that the 0-day bot can
automatically test posted mailing list patches against the right tree.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>