ahci: fix hang on failed softreset

ahci: fix hang on failed softreset

ahci_do_softreset() compared the current time and deadline in reverse
when calculating timeout for SRST issue.  The result is that if
@deadline is in future, SRST is issued with 0 timeout, which hasn't
caused any problem because it later waits for DRDY with the correct
timeout.  If deadline is already exceeded by the time SRST is about to
be issued, the timeout calculation underflows and if the device
doesn't respond, timeout doesn't trigger for a _very_ long time.

Reverse the incorrect comparison order.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Anssi Hannula <anssi.hannula@iki.fi>
Tested-by: Gwendal Grignou <gwendal@google.com>
Cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>