libxl: make libxl__need_xenpv_qemu() operate on domain config

libxl: make libxl__need_xenpv_qemu() operate on domain config

libxl__need_xenpv_qemu() is called with configuration data for console,
vfbs, disks and channels today in order to evaluate the need for
starting a device model for a pv domain.

The console data is local to the caller and setup in a way to never
require a device model. All other data is taken from the domain config
structure.

In order to support other device backends via qemu change the interface
of libxl__need_xenpv_qemu() to take the domain config structure as
input instead of the single device arrays.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>