tegra: move to common SPL framework

Change tegra SPL to use common SPL framework.  Any tegra specific
initialization is now done in spl_board_init() instead of
board_init_f()/board_init_r().  Only one SPL boot target is supported
on tegra, which is boot to RAM image.  jump_to_image_no_args() must be
overridden on tegra so the host CPU can be initialized.

Signed-off-by: Allen Martin <amartin@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Lucas Stach <dev@lynxeye.de>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>