staging:usbip:stub_rx.c: Remove warning quoted string split across lines

This patch removes the checkpatch.pl warnings "quoted string split
across lines" in stub_rx.c by merging the quoted strings and the
ensuring that the lines are not more than 80 characters long.

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