kconfig: Remove no-op selects of choice symbols

Selecting a choice symbol is always a no-op, and the latest version of
Kconfiglib prints a warning. This commit removes all selects of choice
symbols, which might make the Kconfig files a bit clearer and gets rid
of the warnings.

This is just a dumb removal. I did not try to guess the intent of each
select.

Fixes #6849

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>