vendorcode/siemens: Add hwilib for Siemens specific info struct

vendorcode/siemens: Add hwilib for Siemens specific info struct

Add a library which unifies access to Siemens specific hardware information
data. This library is meant to be used with Siemens platforms and can be
selected in Kconfig. The needed source of information has to be present
in cbfs.
This lib can be used in romstage and ramstage.

Change-Id: I2c6e003b0c123b4cf6a84906c2b133b8c38c8b1a
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/14505
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)