msm: socinfo: Add hardware platform id for STP

The default CDT value for the Self-hosting Test Platform
reveals a platform with ID of 23. Add this value to the hw
platform list so that hw_platform sysfs node reports the
correct platform name.

Change-Id: Iaff0e1410a6234aa88a823e03e9cee34b382e783
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>