backport: move kconfig code to "kconf" directory

Having the kconfig code in a directory called "kconfig"
and having a file called "Kconfig" causes issues if the
code is ever stored on a case-insensitive filesystem.
Avoid these by just calling the kconfig directory kconf
instead.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>