merrifield: added early printk support for debug UART

merrifield: added early printk support for debug UART

BZ: 25951

Currently we have 3 types of early printk consoles: max3110 SPI-UART, HSU and PTI.
PTI is awlays supported because it's a Soc debugging feature.
HSU is always supported but also depends on board design. Some boards don't have
HSU UART pins routed to the connector so we can't use it.
Max3110 SPI-UART is a stand-alone chip with SPI interface located in the debug card.
Drivers can access to this chip via Soc's SPI controller or SSP controller(working
in SPI mode).

Previously for mrst, mdfld and clv, max3110 was connected to SPI controller,
but for mrfld, max3110 is connected to SSP controller. This patch is to enable the
early printk console via the SSP controller.

Change-Id: I8ea0e39cd0cb1f2eca3785854fed878f46d9aa1d
Signed-off-by: Mark F. Brown <mark.f.brown@intel.com>
Signed-off-by: Claude Brouat <claude.brouat@intel.com>
Signed-off-by: Bin Gao <bin.gao@intel.com>
Reviewed-on: http://android.intel.com:8080/37359
Reviewed-by: Ng, Cheon-woei <cheon-woei.ng@intel.com>
Tested-by: Ng, Cheon-woei <cheon-woei.ng@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>