Revert "Added local directory as source of kernel code"

Revert "Added local directory as source of kernel code"

This reverts commit 73da2ff6f718f2889e3c5024d899f8d58f502863.

The reason for adding support for a local location was to be able to do
development on the Linux kernel source tree on a local directory rather
than have to clone it for every build.

We already have a mechanism for that, it's called override-srcdir. It's
been available since September 2011, more than a year before this patch
was committed.

Otherwise, we're going to be adding support for local sources in other
packages. First was U-Boot as submitted by Adam. But what next? We can't
have such support for all packages, especially since override-srcdir
does the job.

Besides, using a local source tree makes the build non-reproducible, so
we don't really want to have this in a .config (or defconfig).

We only handle the boolean option in legacy, as there is nothing we can
do with the directory path.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Rafal Fabich <rafal.fabich@gmail.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>