usb: drop HOST_USB

Nowdays we use libusb for usb-host, so we don't have different code
for linux vs. bsd any more.  So there is little reason to have the
HOST_USB variable, we can just write things directly into the Makefile
and avoid a pointless indirection.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Message-id: 20170908111217.21985-2-kraxel@redhat.com

configure

@@ -5967,13 +5967,6 @@ if test "$live_block_migration" = "yes" ; then
   echo "CONFIG_LIVE_BLOCK_MIGRATION=y" >> $config_host_mak
 fi
 
-# USB host support
-if test "$libusb" = "yes"; then
-  echo "HOST_USB=libusb legacy" >> $config_host_mak
-else
-  echo "HOST_USB=stub" >> $config_host_mak
-fi
-
 # TPM passthrough support?
 if test "$tpm" = "yes"; then
   echo 'CONFIG_TPM=$(CONFIG_SOFTMMU)' >> $config_host_mak

hw/usb/Makefile.objs

@@ -38,7 +38,11 @@ endif
 common-obj-$(CONFIG_USB_REDIR) += redirect.o quirks.o
 
 # usb pass-through
-common-obj-y += $(patsubst %,host-%.o,$(HOST_USB))
+ifeq ($(CONFIG_LIBUSB),y)
+common-obj-y += host-libusb.o host-legacy.o
+else
+common-obj-y += host-stub.o
+endif
 
 ifeq ($(CONFIG_USB_LIBUSB),y)
 common-obj-$(CONFIG_XEN) += xen-usb.o