This moves the query_ports() and get_port_state() to be shared memory
lookups.

The hal_client.c file now accesses shared memory at init time, and
performes the two functions above by looking in shared memory.

The thing is sill suboptimal, because the "exported" hexp_port_state_t
structure is only slightly different from struct hal_port_state. And
most fields being looked up are never filled.

Last but not least, halexp_get_timing_state() is not ready to be
converted to shared memory at this point in time (timing data is not
stored to shmem yet).

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