[PATCH] libata: fix ata_qc_issue() error handling

When ata_qc_issue() fails, the qc might have been dma mapped or not.
So, performing only ata_qc_free() results in dma map leak.  This patch
makes ata_qc_issue() mark dma map flags correctly on failure and calls
ata_qc_complete() after ata_qc_issue() fails.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>