h2200: Fix build error

h2200: Fix build error

Commit <8bfc288c3955> ("usb: gadget: ether: Perform board
initialization from ethernet gadget driver") added board_usb_init
and board_usb_cleanup in ethernet gadget driver. But h2200 board
didn't have board_usb_init and board_usb_cleanup implementations.

This introduced the following build errors
+drivers/usb/gadget/built-in.o: In function `usb_eth_halt':
+drivers/usb/gadget/ether.c:2498: undefined reference to `board_usb_cleanup'
+drivers/usb/gadget/built-in.o: In function `usb_eth_init':
+drivers/usb/gadget/ether.c:2316: undefined reference to `board_usb_init'

Fix it here by adding empty board_usb_init and board_usb_cleanup
functions in h2200.c.

Fixes: <8bfc288c3955> ("usb: gadget: ether: Perform board
initialization from ethernet gadget driver")

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>