drm: fix build with UDL if USB is a module

reported by sfr on -next merge.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 7f20297..ed407cc 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -12,8 +12,9 @@
 		drm_platform.o drm_sysfs.o drm_hashtab.o drm_mm.o \
 		drm_crtc.o drm_modes.o drm_edid.o \
 		drm_info.o drm_debugfs.o drm_encoder_slave.o \
-		drm_trace_points.o drm_global.o drm_usb.o
+		drm_trace_points.o drm_global.o
 
+drm-$(CONFIG_USB) += drm_usb.o
 drm-$(CONFIG_COMPAT) += drm_ioc32.o
 
 drm_kms_helper-y := drm_fb_helper.o drm_crtc_helper.o drm_dp_i2c_helper.o
diff --git a/drivers/gpu/drm/drm_usb.c b/drivers/gpu/drm/drm_usb.c
index 445003f..c8c83da 100644
--- a/drivers/gpu/drm/drm_usb.c
+++ b/drivers/gpu/drm/drm_usb.c
@@ -2,7 +2,6 @@
 #include <linux/usb.h>
 #include <linux/export.h>
 
-#ifdef CONFIG_USB
 int drm_get_usb_dev(struct usb_interface *interface,
 		    const struct usb_device_id *id,
 		    struct drm_driver *driver)
@@ -115,4 +114,3 @@
 	usb_deregister(udriver);
 }
 EXPORT_SYMBOL(drm_usb_exit);
-#endif