kconfig: Turn pointless/confusing 'menuconfig's into 'config's

Defining a symbol with 'menuconfig' just tells the menuconfig to display
any dependent symbols that immediately follow it in a separate menu.
'menuconfig' has no effect on symbol values.

Making a symbol that doesn't have any dependent symbols after it a
'menuconfig' should be avoided, because then you end up with an empty
menu, which is shown as e.g.

    [*] Enable foo ---

This is how it would be shown if there were children but they all
happened to be invisible as well.

With a regular 'config', it turns into

    [*] Enable foo

Change all pointless 'menuconfig's to 'config's.

See the section on 'menuconfig' on the Kconfig - Tips and Best Practices
page as well.

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