package/libevdev: add dependency on host-python

libevdev needs python to generate a header file. We can't rely on the
1system pPython, since it may be too old (missing argparse in python
2.6).

Fixes:
    http://autobuild.buildroot.net/results/1f5c0689ae129ae5fa30f31a4f47ccbd7705ff00/
    http://autobuild.buildroot.net/results/1729043d9c977a59a4fdd7ccd3d16cfc8aef7678/
    http://autobuild.buildroot.net/results/3ab080e96576e0012fea853009811247338e665e/



Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>