net: rfkill: gpio: clean up clock handling

Use a simple flag to see the state of the clock, and make
the clock available even without a name. Also, get rid of
HAVE_CLK dependency.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Rhyland Klein <rklein@nvidia.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>