usb: gadget: Fix checkpatch error for braces

Fix error message by checkpath.pl
open brace '{' following struct/enum go on the same line

Patch applied by running fix inplace capability of checkpatch:
checkpatch.pl -f *.[ch] --types OPEN_BRACE --fix-inplace

Signed-off-by: Anson Jacob <ansonjacob.aj@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>