Input: tegra-kbc - add tegra keyboard driver

This patch adds support for the internal matrix keyboard controller for
Nvidia Tegra platforms.

Signed-off-by: Rakesh Iyer <riyer@nvidia.com>
Reviewed-by: Trilok Soni <tsoni@codeaurora.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>