tegra: spi: pull register structs out of headers

Move register structs from headers into .c files and use common name.
This is in preparation of making common fdt front end for SPI
drivers.

Signed-off-by: Allen Martin <amartin@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>