plum-MA: dts: add RS485 TxEnable/RxEnable resources.

(cherry picked from commit e74ef54f668b5956dad1771c573ee986c2d6c5cb)
plum-MA: dts: add alias for xio_04 (UART/D16).

(cherry picked from commit 6d998e6abcaf80c3328cc7cf4841f5dd5114da65)
serial: 8250: add support for RS-485 mode.

(cherry picked from commit e0ed22bf02cf26078778a65bdabdbc093b59dc9a)
firmware: add am335x power-management firmware.
plum-MA: update default config.
Merge branch 'devel/rs485' into MA-E3xx/linux-3.13.y