qemu_capabilities: Add QEMU_CAPS_USB_HOST_HOSTDEVICE

qemu_capabilities: Add QEMU_CAPS_USB_HOST_HOSTDEVICE

This capability tracks whether "usb-host" device has "hostdevice"
attribute. This attribute allows us to specify full path to the
USB device ("/dev/bus/usb/$bus/$dev") but more importantly, since
QEMU uses qemu_open() for this attribute it allows us to pass
pre-opened FD and have QEMU not bother with opening the file at
all.

The attribute was added in v5.1.0-rc0~71^2~1 QEMU commit.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>