ARM: tegra: remove "Tegra board type" comment from Kconfig

Since the complete conversion to device tree, there are no board-
specific Kconfig options left, so remove the useless Kconfig entry.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Olof Johansson <olof@lixom.net>