Add Merrifield HVP board type support

Add Merrifield HVP board type support

BZ: 30074

Merrifield HVP board is different from Merrifield VP board in
quite a few components, such as storage, usb, audio and so on.
So it's necessary to add a new macro in kernel board type for
Merrifield HVP.

This patch add a new board type macro CONFIG_BOARD_MRFLD_HVP
for Merrifield HVP board and also creat a new board specific
file board-hvp.c for HVP board specific.

Change-Id: Iaac388518979dae4df7d24062572e926d3d54aed
Signed-off-by: Yunpeng Gao <yunpeng.gao@intel.com>
Reviewed-on: http://android.intel.com:8080/42033
Reviewed-by: Tang, Richard <richard.tang@intel.com>
Reviewed-by: Brouat, Claude <claude.brouat@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>