xserver-xf86-config: remove obsolete configuration files

xserver-xf86-config: remove obsolete configuration files

For reasons we have explicit xorg.conf files for a number of the qemu
machines, but not all of them. These mainly disabled screen blanking
(which is now down with a separate fragment) but also explictly set the
device driver to fbdev which meant they didn't use the modesettings
driver as they should (with the virtio framebuffer from qemu).

This is the root cause of why the xserver 21.1.16 upgrade doesn't work
on a number of machines: the /sys probing changed and the fbdev driver
now refuses to use the PCI framebuffer device as there are better
drivers, but we've explictly told xorg to use the wrong driver.

For more details, see https://gitlab.freedesktop.org/xorg/xserver/-/issues/1798.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>