Fix libusb-1.0.22 deprecated libusb_set_debug with libusb_set_option

Fix libusb-1.0.22 deprecated libusb_set_debug with libusb_set_option

libusb-1.0.22 marked libusb_set_debug deprecated
it is replaced with
libusb_set_option(libusb_context, LIBUSB_OPTION_LOG_LEVEL, libusb_log_level);

details here: https://github.com/libusb/libusb/commit/539f22e2fd916558d11ab9a66f10f461c5593168

Warning here:

  CC      hw/usb/host-libusb.o
/builds/xen/src/qemu-xen/hw/usb/host-libusb.c: In function 'usb_host_init':
/builds/xen/src/qemu-xen/hw/usb/host-libusb.c:250:5: error: 'libusb_set_debug' is deprecated: Use libusb_set_option instead [-Werror=deprecated-declarations]
     libusb_set_debug(ctx, loglevel);
     ^~~~~~~~~~~~~~~~
In file included from /builds/xen/src/qemu-xen/hw/usb/host-libusb.c:40:0:
/usr/include/libusb-1.0/libusb.h:1300:18: note: declared here
 void LIBUSB_CALL libusb_set_debug(libusb_context *ctx, int level);
                  ^~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make: *** [/builds/xen/src/qemu-xen/rules.mak:66: hw/usb/host-libusb.o] Error 1
make: Leaving directory '/builds/xen/src/xen/tools/qemu-xen-build'

Signed-off-by: John Thomson <git@johnthomson.fastmail.com.au>
Message-id: 20180405132046.4968-1-git@johnthomson.fastmail.com.au
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 9d8fa0df49af16a208fa961c2968fba4daffcc07)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>