Staging: xillybus: quoted strings split across lines

Fix checkpatch.pl issues with quoted strings split across lines in xillybus_core.c

Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>