iwlwifi: add testmode cmd IWL_TM_CMD_APP2DEV_GET_FW_INFO

Add new testmode command IWL_TM_CMD_APP2DEV_GET_FW_INFO for
reporting the following information of existing loaded uCode image.
+ uCode type
+ Instruction section size
+ Data section size

Signed-off-by: Kenny Hsu <kenny.hsu@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>