libsoup: add gnome-keyring dependency.

libsoup: add gnome-keyring dependency.

libsoup's configure.in added a gnome-keyring check since the last version.

Failure looks like this:

| checking whether to build libsoup-gnome... yes
| checking for GNOME_KEYRING... no
| configure: error: Could not find gnome-keyring devel files.
| Configure with --without-gnome if you wish to build only libsoup
| without GNOME-specific features.
| FATAL: oe_runconf failed`
Signed-off-by: Holger Hans Peter Freyther <zecke@selfish.org>