mwifiex: don't leak DMA command skbuffs

mwifiex: don't leak DMA command skbuffs

The current mwifiex pcie driver assumed that it would get
its cmdrsp_complete() callback called before another command
was sent to unmap the command's skbuff. However, that is not
true. The mwifiex_check_ps_cond() will send a sleep command
to the card without having adapter->curr_cmd set. Within the
workqueue's state machine the adapter's state would be set
to allow commands (curr_cmd = NULL && cmd_sent = false) after
having receieved the response from the sleep command. The
card->cmd_buf would then be overridden with the new command
but the first command's skbuff was not unmapped. This leaks
mapped skbuffs when a bounce buffer is employed.

To rectify this unmap the card->cmd_buf when the response is
received from the card instead of waiting for the
cmdrsp_complete() callback.

Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Reviewed-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>