libxl: Remove qxl support for the 4.3 release

libxl: Remove qxl support for the 4.3 release

The qxl drivers for Windows and Linux end up calling instructions
that cannot be used for MMIO at the moment.  Just for the 4.3 release,
remove qxl support.

This patch should be reverted as soon as the 4.4 development window opens.

The issue in question:

(XEN) emulate.c:88:d18 bad mmio size 16
(XEN) io.c:201:d18 MMIO emulation failed @ 0033:7fd2de390430: f3 0f 6f
19 41 83 e8 403

The instruction in question is "movdqu (%rcx),%xmm3".  Xen knows how
to emulate it, but unfortunately %xmm3 is 16 bytes long, and the interface
between Xen and qemu at the moment would appear to only allow MMIO accesses
of 8 bytes.

It's too late in the release cycle to find a fix or a workaround.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>