crypto: qat - fix firmware loading failure for GEN6 devices

crypto: qat - fix firmware loading failure for GEN6 devices

QAT GEN6 hardware requires a minimum 3 us delay during the acceleration
engine reset sequence to ensure the hardware fully settles.
Without this delay, the firmware load may fail intermittently.

Add a delay after placing the AE into reset and before clearing the reset,
matching the hardware requirements and ensuring stable firmware loading.
Earlier generations remain unaffected.

Fixes: 17fd7514ae68 ("crypto: qat - add qat_6xxx driver")
Signed-off-by: Suman Kumar Chakraborty <suman.kumar.chakraborty@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>