configs/teliv_evk_pro3: remove defconfig

configs/teliv_evk_pro3: remove defconfig

This defconfig fails to build with gcc 6.x, even though we switched to
using gcc 6.x as the default gcc version in May 2017.

It hasn't been updated since April 2017, and the original submitter,
Fabio Porcedda said:

  Unfortunately a newer kernel doesn't boot and I don't have the time
  to fix the issue. If having a defconfig that doesn't build on gcc
  6.x is unacceptable feel free to remove it.

So, let's get rid of this defconfig, which will remove the following
build error:

  https://gitlab.com/buildroot.org/buildroot/-/jobs/55306952

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 13fb1c49128d4c039fc23fcf32317008862f8b4b)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>