diag: Add support for diag feature query command

The Diag Feature Query Command is intended to be used to
communicate feature differences of specific devices that
may impact interaction with a host tool. The patch adds
support for the same command.

Change-Id: I4f0a8ac6b609692eb94849104da61465719822c2
Signed-off-by: Hardik Arya <harya@codeaurora.org>