Tegra: spe: shared console for Tegra platforms

Tegra: spe: shared console for Tegra platforms

There are Tegra platforms which have limited UART ports and so
all the components have to share the console. The SPE helps out
by collecting all the logs in such cases and prints them on the
shared UART port.

This patch adds a driver to communicate with the SPE driver, which
in turn provides the console.

Change-Id: Ie750520b936b8bed0ab1d876f03fc0a3490a85a3
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>