This patch check output of pci_map_single() calls. I missed them on
my previous patch "iwlegacy: check for dma mapping errors", which
fixed only pci_map_page() calls.

To handle remaining possible dma mappings errors, we need to rearrange
ilXXXX_tx_skb() and il_enqueue_hcmd() functions.
Signed-off-by: NStanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>