regmap: fix a couple of typos

These sentences are not proper English due to the typos. I had initially caught
one of them while trying to understand the regmap feature, and then I just ran
the vim spell checker, and went through all the items that would need to be
fixed for this header file.

Signed-off-by: Laszlo Papp <lpapp@kde.org>
Signed-off-by: Mark Brown <broonie@linaro.org>