ARM: tegra: move NVIDIA common files to arch/arm/mach-tegra

ARM: tegra: move NVIDIA common files to arch/arm/mach-tegra

All the Tegra boards borrow the files from board/nvidia/common/
directory, i.e., board/nvidia/common/* are not vendor-common files,
but SoC-common files.

Move NVIDIA common files to arch/arm/mach-tegra/ to clean up
Makefiles.

As arch/arm/mach-tegra/board.c already exists, this commit renames
board/nvidia/common/board.c to arch/arm/mach-tegra/board2.c,
expecting they will be consolidated as a second step.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Tom Warren <twarren@nvidia.com>
Cc: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>