The current implementation is broken for regmaps that have a reg_stride,
since it doesn't take the stride into account. Correct this by using the
helper function to calculate the register offset.

Fixes: f01ee60f ("regmap: implement register striding")
Signed-off-by: NCharles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: NMark Brown <broonie@kernel.org>