ARM: tegra: don't request GPIO from Seaboard's SPL

Seaboard has a GPIO that switches an external mux between Tegra's debug
UART and SPI flash. This is initialized from the SPL so that SPL debug
output can be seen. Simplify the code that does this, and don't actually
request the GPIO in the SPL; just program it. This saves ~4.5K from the
size of the SPL, mostly BSS due to the large gpio_names[] table that is
no longer required. This makes Seaboard's SPL fit within the current max
size.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>
Acked-by: Allen Martin <amartin@nvidia.com>
Tested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>