kconfig: Global whitespace/consistency cleanup

Clean up space errors and use a consistent style throughout the Kconfig
files. This makes reading the Kconfig files more distraction-free, helps
with grepping, and encourages the same style getting copied around
everywhere (meaning another pass hopefully won't be needed).

Go for the most common style:

 - Indent properties with a single tab, including for choices.

   Properties on choices work exactly the same syntactically as
   properties on symbols, so not sure how the no-indentation thing
   happened.

 - Indent help texts with a tab followed by two spaces

 - Put a space between 'config' and the symbol name, not a tab. This
   also helps when grepping for definitions.

 - Do '# A comment' instead of '#A comment'

I tweaked Kconfiglib a bit to find most of the stuff.

Some help texts were reflowed to 79 columns with 'gq' in Vim as well,
though not all, because I was afraid I'd accidentally mess up
formatting.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>