USB: Remove the duplicate definition of HUB_SET_DEPTH

The macro HUB_SET_DEPTH is defined twice in ch11.h (introduced by
commit 0eadcc09 "usb: USB3.0 ch11 definitions" and dbe79bbe "USB 3.0
Hub Changes"), so remove the duplicate one in the USB 2.0 part.

Signed-off-by: Qinglin Ye <yestyle@gmail.com>
Cc: John Youn <John.Youn@synopsys.com>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>