libxl: fix HVM vNUMA

libxl: fix HVM vNUMA

This patch does two thing:

The original code erroneously fills in xc_hvm_build_args before
generating vmemranges. The effect is that guest memory is populated
without vNUMA information. Move the hunk to right place to fix this.

Move the subtraction of video ram to libxl__vnuma_build_vmemrange_hvm
because it's the central place for generating vmemranges.

Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>