soc: qcom: socinfo: Add support for HDK platform

Add socinfo support for HDK(Hardware Development Kit)
platform so that /sys/devices/soc0/hw_platform shows
it is HDK device.

Change-Id: Ibf85529b342d89530bb5c298bbb5f052122b906d
Signed-off-by: Tengfei Fan <tengfeif@codeaurora.org>