ARM: tegra: export Tegra chipid

The powergating and reset handling code needs to differentiate between Tegra
variants. Therefore we export the chipid here.

Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>