ssa_db.[c h]: Misc fixes

 - ssa_db_create: calloc() is used instead of malloc()
 - ssa_db_create: p_ssa_db initialization to NULL is removed
 - Typos and indentations fixes

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