ds2490.c: Add required spaces

Add missing spaces in for- and while-loops
reported missing 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>