ARM: tegra210: p3450: fix Jetson Nano SPI flash

ARM: tegra210: p3450: fix Jetson Nano SPI flash

The Nano's SPI flash stopped working in U-Boot, as the prior stage loaded
U-Boot, the only thing it was used for was save/loading env vars so update
the DT so it can now initialise it. It also drops enabling the old
TEGRA114_SPI driver, as the flash hangs off the faster TEGRA210_QSPI
interface, nothing on the Nano uses the old interface by default so it's
surplus.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Svyatoslav Ryhel <clamor95@gmail.com>
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>