libertas: fix handling of command timeout, completion and interruption

When commands time out, corruption ensues. As lbs_complete_command()
is called without locking, the command node is mistakenly freed twice.
Also fixed up locking here in a few other places.

The nature of command timeout may be that the card didn't even
acknowledge receipt of the request. Detect this case and reset dnld_sent
so that other commands don't hang forever.

When cmdnodes are moved between the free list and the pending list,
their list heads should be reinitialized. Fixed this.

Sometimes commands are completed without actually submitting them or
removing them from cmdpendingq. We must remember to remove them from
cmdpendingq in these cases, so handle this in lbs_complete_command().

Harmless signals generated during suspend/resume were interrupting
lbs_cmd. Convert to an uninterruptible sleep to avoid this.

lbs_thread must be woken up every time there is some new work to do.
I found that when 2 commands are queued, ther completion of the first
command would not wake up lbs_thread to submit the second. Poke lbs_thread
at the end of lbs_complete_command() to fix this.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>