usb: gadget: Makefile: remove ccflags-y

No header file used from udc directory, so remove line below
ccflags-y += -I$(srctree)/drivers/usb/gadget/udc.

Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Link: https://lore.kernel.org/r/1647333751-32367-1-git-send-email-quic_linyyuan@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/Makefile

@@ -4,7 +4,6 @@
 #
 subdir-ccflags-$(CONFIG_USB_GADGET_DEBUG)	:= -DDEBUG
 subdir-ccflags-$(CONFIG_USB_GADGET_VERBOSE)	+= -DVERBOSE_DEBUG
-ccflags-y				+= -I$(srctree)/drivers/usb/gadget/udc
 
 obj-$(CONFIG_USB_LIBCOMPOSITE)	+= libcomposite.o
 libcomposite-y			:= usbstring.o config.o epautoconf.o