connman: disable for static builds

It needs dlopen(), otherwise it will fail at the configure phase with a
message like this one:

checking for dlopen in -ldl... no
configure: error: dynamic linking loader is required

Fixes:
  http://autobuild.buildroot.net/results/647/64742a1d3a07f86a7c801da5ef30892c1f760031/



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>