ds2490.c: Move struct open braces to previous line

Move open braces of two structs to the declaration line,
as criticized by checkpatch.

Signed-off-by: Henriette Hofmeier <passt@h-hofmeier.de>
Signed-off-by: Florian Harbecke <florian.harbecke@fau.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>