serial: serial_octeon_pcie_console.c: Add PCI remote console support

This patch adds the PCI remote console feature for MIPS Octeon, which
will be used by the upcoming Octeon III NIC23 board support. It enables
the use of the "oct-remote-console" tool on host PC's to communicate
with the PCIe target.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Aaron Williams <awilliams@marvell.com>
Cc: Chandrakala Chavva <cchavva@marvell.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>