staging:usbip:usbip_common.c: Join quoted string split accross lines

This patch removes the checkpatch.pl warnings "quoted string split accross lines"
in usbip_common.c.

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>