crypto: qat - add shutdown handler to qat_c3xxx

During a warm reset via kexec, the system bypasses the driver removal
sequence, meaning that the remove() callback is not invoked.
If a QAT device is not shutdown properly, the device driver will fail to
load in a newly rebooted kernel.

This might result in output like the following after the kexec reboot:

    QAT: AE0 is inactive!!
    QAT: failed to get device out of reset
    c3xxx 0000:3f:00.0: qat_hal_clr_reset error
    c3xxx 0000:3f:00.0: Failed to init the AEs
    c3xxx 0000:3f:00.0: Failed to initialise Acceleration Engine
    c3xxx 0000:3f:00.0: Resetting device qat_dev0
    c3xxx 0000:3f:00.0: probe with driver c3xxx failed with error -14

Implement the shutdown() handler that hooks into the reboot notifier
list. This brings down the QAT device and ensures it is shut down
properly.

Cc: <stable@vger.kernel.org>
Fixes: 890c55f4 ("crypto: qat - add support for c3xxx accel type")
Reviewed-by: Ahsan Atta <ahsan.atta@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>