Alpha Networks SNQ60A0_320F: Remove Demo OS partition work around

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Add more dependencies to debian-prepare-build-host target

Issue #39:
The following missing dependencies were added:

* libncurses5
* libncurses5-dev
* bc

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>