Making the header subfields members of struct dvfs_info allows to make
the code better readable and avoids some macro magic.

In addition remove a useless statement using info->latency.
Tested-by: NKevin Hilman <khilman@baylibre.com>
Signed-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>