libsoup: add missing dependency on host-intltool

Fixes:

  http://autobuild.buildroot.net/results/e24/e240828ed2fdeb98f36818c0ef19b15dadc2e59f/build-end.log



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>