regmap: Fixup the kernel-doc comments on functions/structures

Most of the kernel-doc comments in regmap don't actually generate
correctly. This patch fixes up a few common issues, corrects some typos
and adds some missing argument descriptions.

The most common issues being using a : after the function name which
causes the short description to not render correctly and not separating
the long and short descriptions of the function. There are quite a few
instances of arguments not being described or given the wrong name as
well.

This patch doesn't fixup functions/structures that are currently missing
descriptions.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>