iwlwifi: Fix get_cmd_string() for REPLY_3945_RX

0x1b is a 3945 specific command, we should print it too when debugging.

Signed-off-by: Samuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>