Enable SLINK4 and connected device in Tegra30 based
platform Cardhu.
Setting maximum spi frequency to 25MHz.

SPI serial flash is connected on CS1 of SLINK4 on
cardhu platform.
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
[swarren: swapped reg/compatible order to be consistent]
Signed-off-by: Stephen Warren <swarren@nvidia.com>