botan: fix static build

see http://autobuild.buildroot.net/results/2d1/2d1563e253b669b45c9df449c5b3a750c04a43dc/

this commit reverts the previous commit 84047394ed6ad08adb9f59a9022553a327eef040
which disables static build in Config.in

the option --no-autoload prevents the use of the function dlopen.

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>