MAINTAINERS: add USB gadget regex to u-boot-dfu tree

We try to split work with Marek on USB as following:
- Mattijs handles USB gadget
- Marek handles the rest of USB

Add additional gadget patterns to the maintainers file so that I
get cc'ed more often on USB gadget patches.

Acked-by: Marek Vasut <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mattijs Korpershoek <[email protected]>

MAINTAINERS

@@ -1017,8 +1017,11 @@ F:	common/update.c
 F:	doc/api/dfu.rst
 F:	doc/usage/dfu.rst
 F:	drivers/dfu/
+F:	drivers/usb/*/*gadget*
 F:	drivers/usb/gadget/
 F:	include/dfu.h
+F:	include/linux/usb/ch9.h
+F:	include/linux/usb/gadget.h
 
 DRIVER MODEL
 M:	Simon Glass <[email protected]>