ARM: tegra: enable 8-bit SD slots in board files

Harmony contains an SD slot with all 8 bits routed. This allows plugging
in an eMMC-chip-in-SD-form-factor.

Seaboard/Springbank/Ventana/AC100 all have an eMMC chip with all 8 bits
hooked up.

Now that the U-Boot eMMC code fully supports 8-bit operation, initialize
those ports as 8-bit instead of 4-bit to improve performance.

Whistler was already registering its ports as 8-bit.

TrimSlice doesn't have any 8-bit ports.

I don't have any Avionic Design boards nor the Colibri board to test with.

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