regulator: fix calculation of voltage range in da9034_set_ldo12_voltage()

For val to be greater than 7 or less than 20 is logically always true.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Liam Girdwood <lrg@slimlogic.co.uk>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>