iwlwifi: fix Tx cmd memory allocation failure handling

This patch "iwlwifi: do not use GFP_DMA in iwl_tx_queue_init" removes
GFP_DMA from allocation tx command buffers. GFP_DMA allows allocation
only for memory under 16M which causes allocation problems
suspend/resume flows.

Using kmalloc is temporal solution and some consistent/coherent
allocation schema will be more correct. Since iwlwifi hardware
supports 64bit address this solution should work on x86 (32 and
64bit) for now.

This patch fixes memory freeing problem in the previous patch.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Ian Schram <ischram@telenet.be>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>