Instead of putting object files inside libzephyr.a,
simply build a separate static library as most other
driver types are doing this already.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
It is useful that the ptp_clock_get() function can be called from
the userspace. Create also unit test for calling that function
from userspace.
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>