am33xx: Update DT files, add am335x_gp_evm_config target

- Re-sync DT files for am33xx with Linux Kernel v4.1
- Include DT file now for the "AM335x GP EVM" and build target for it,
  via device tree and DM.
- We only need to provide platform data for UART when OF_CONTROL isn't
  also enabled really.  We can just push GPIO to coming from DT

Signed-off-by: Tom Rini <trini@konsulko.com>