Staging: usbip: fix space before tab in usbip_common.h

This is a patch  to the usbip_common.h fix space before tab
warning found by the checkpatch.pl tools
Signed-off-by: Ruslan Pisarev <ruslan@rpisarev.org.ua>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>