gr-osmosdr: add host-python-cheetah dependency

Since b7f1b030 host-python-cheetah is no more a
dependency for gnuradio. So this package must be explicitly added for
gr-osmosdr.

Fix : http://autobuild.buildroot.net/results/aa208a69996548c15d937fc7c97d267162a56c48/



Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>