Merge changes I8990bce2,Iacef5e67,I2976c0a4,I8551a802 into integration

* changes:
  fix(plat/marvell/a3720/uart): do external reset during initialization
  feat(plat/marvell/a3k): add north and south bridge reset registers
  fix(plat/marvell/a3720/uart): configure UART after TX FIFO reset
  feat(plat/marvell/a3720/uart): preserve x1/x2 regs in console_a3700_core_init()