ssa.c: Add prdb_calc_in_progress flag into ssa_access_handler

when PRDBs are being recalculated due to SMDB update

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: Support update pending (for SMDB) in access layer

Change ssa_downstream_smdb_update_ready to return 1 if PRDB calculation
is in progress

Access will send DB update ready message to extract/core threads
when appropriate.

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: Support prdb_calc_in_progress and update pending on SSA_CONN_DONE message receipt in access handler

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: Remove unneeded argument from ssa_access_smdb_update_ready internal API

Signed-off-by: Hal Rosenstock <hal@mellanox.com>