usb: gadget: Use correct include style for local headers

Local headers should always use "" and not <>.  Fixes the following error:

 drivers/usb/gadget/configfs.c:19:28: fatal error:
	function/u_ncm.h: No such file

Fixes: 9b8c89e9 ("usb: gadget: Send dedicate uevent for ML client connection")
Change-Id: Ic0dedbad26ddf692396eedeb81820ee806ab7783
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>