docs: kconfig: Fix grammar and formatting

- Remove unnecessary spaces
- Fix grammar s/to solution/solution/

Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>