spi: tegra114: use u32 for 32-bit register values

Previously used “unsigned long” may lead to confusion should the code
be compiled for 64-bit machine.

This commit also removes some unused fields of the tegra_spi_data
structure as well as removes duplicated #defines.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>