Add support for Intel Avoton to i801 SMBus driver

Add support to the i801 SMBus driver for the Intel Avoton CPU family.
Make serial port and console flag be able to customize

Accton AS5712_54X uses COM2 as serial port. And it needs to turn
on the flag of console to make syslinux boot menu be visible.

This patch provides additional variables to configure the settings.

Reference:
1. http://www.syslinux.org/wiki/index.php/SYSLINUX#CONSOLE_flag_val
2. http://www.syslinux.org/wiki/index.php/SYSLINUX#SERIAL_port_.5Bbaudrate_.5Bflowcontrol.5D.5D

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
QuantaMesh 1000 Series T1048-LB9

================================================================================
 - 1G/10G Datacenter & Enterprise-Class Ethernet switch
 - 48 10Base-T/100Base-TX/1000Base-T ports
 - 4 1GbE/10GbE dual speed SFP+ slots
 - 1 RJ-45 out-of-band management port (10/100/1000M)
 - 1 RJ-45 console port

  How to compile ONIE
================================================================================
  $ cd onie/machine/quanta/quanta_lb9
  $ ./build.sh all

  How to compile demo installer
================================================================================
  $ cd onie/machine/quanta/quanta_lb9
  $ ./build.sh demo

  How to compile documents
================================================================================
  $ cd onie/machine/quanta/quanta_lb9
  $ ./build.sh docs

For further information, please take a look at ``machine/quanta/quanta_lb9/INSTALL``

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>