tegra: Add flow, gp_padctl, fuse, sdram headers

These headers provide access to additional Tegra features.

flow - start/stop CPUs
sdram - parameters for SDRAM
fuse - access to on-chip fuses / security settings
gp_padctl - pad control and general purpose registers

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Yen Lin <yelin@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>