The HAL process, in the white rabbit switch, is now exporting data
structures in shared memory. Thus, we don't need to "get_port_state"
by RPC, and accessing shared memory is enough.  This change in ppsi
involves the following changes:

arch-wrs/wrs-startup.c: offer global hal_ports[] for others to use
(yes, globals are bad, I know...)

arch-wrs/include/ppsi-wrs.h: provide pp_wrs_lookup_port

time-wrs/wrs-socket.c: use shmem. This means some values are now
hardwired as constants, because they were passed as such from the hal.

arch-wrs/main-loop.c: verify link up or down in the shared mem status

arch-wrs/wrs-calibration.c: wrs_read_calibration_data uses shmem

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>