treewide: use full path to usb/usb_dc.h header

The build infrastructure should not be adding the drivers subdirectory
to the include path.  Fix the legacy uses that depended on that
addition.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>

drivers/usb/device/usb_dc_mcux_ehci.c

@@ -6,7 +6,7 @@
 
 #include <soc.h>
 #include <string.h>
-#include <usb/usb_dc.h>
+#include <drivers/usb/usb_dc.h>
 #include <soc.h>
 #include <device.h>
 #include "usb_dc_mcux.h"

drivers/usb/device/usb_dc_native_posix.c

@@ -12,7 +12,7 @@
 #include <string.h>
 #include <stdio.h>
 #include <sys/byteorder.h>
-#include <usb/usb_dc.h>
+#include <drivers/usb/usb_dc.h>
 #include <usb/usb_device.h>
 #include <net/net_ip.h>
 

drivers/usb/device/usb_dc_nrfx.c

@@ -17,7 +17,7 @@
 #include <string.h>
 #include <stdio.h>
 #include <kernel.h>
-#include <usb/usb_dc.h>
+#include <drivers/usb/usb_dc.h>
 #include <usb/usb_device.h>
 #include <drivers/clock_control.h>
 #include <hal/nrf_power.h>