iwlagn: do not use interruptible waits

Since the dawn of its time, iwlwifi has used
interruptible waits to wait for synchronous
commands and firmware loading.

This leads to "interesting" bugs, because it
can't actually handle the interruptions; for
example when a command sending is interrupted
it will assume the command completed fully,
and then leave it pending, which leads to all
kinds of trouble when the command finishes
later.

Since there's no easy way to gracefully deal
with interruptions, fix the driver to not use
interruptible waits.

This at least fixes the error
iwlagn 0000:02:00.0: Error: Response NULL in  'REPLY_SCAN_ABORT_CMD'

I have seen in P2P testing, but it is likely
that there are other errors caused by this.

Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: stable@kernel.org [2.6.24+]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>