Now that on-chip UARTs each have separate platform_data, the external
UART needs an non-conflicting ID.  Since there are 3 on-chip UARTs,
the Zoom2 external UART will be registered after as the fourth.
Signed-off-by: NVikram Pandita <vikram.pandita@ti.com>
Signed-off-by: NKevin Hilman <khilman@deeprootsystems.com>