iwlwifi: fw api: add DRAM buffer allocation command

Add support code to be able to use the DRAM buffer allocation command,
which allows us to send information about a buffer to the firmware
to use it with the DBGC hardware.

Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>