mtools: fix build when libiconv is enabled
Fixes
http://autobuild.buildroot.net/results/298/
298858b6cc89438dcd044c74dff4231186a065e1/
http://autobuild.buildroot.net/results/7e7/
7e7e7027226bb0251e32a90df2f00d9e84aedaaf/
http://autobuild.buildroot.net/results/c18/
c18e7da16121417e597a153ce7dc2a3b64ece3b0/
http://autobuild.buildroot.net/results/b29/
b29e80441ed87be651d720ae2dccf24d0f7fe8b6/
Signed-off-by: Bernd Kuhls <berndkuhls@hotmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>