usb: message: remove redundant declaration

Fix the Sparse warning:

message.c:1390:21: warning: symbol 'i' shadows an earlier one
message.c:1294:13: originally declared here

Signed-off-by: Kris Borer <kborer@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>