libgnome-keyring: add (from oe-core)

This was in oe-core previously but it's not actually used by anything:
webkit-gtk claimed a false dependency and the new libsoup has removed all use of
gnome-keyring.

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>