iwlwifi: Probe Flow - Performing allocation in a separate function

Performing allocation in a separate function (previously handled in
'probe')

Signed-off-by: Assaf Krauss <assaf.krauss@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>