Documentation: ABI: debugfs-driver-qat: fix fw_counters path

The debugfs description for fw_counters reports an incorrect path
indicating a qat folder that does not exist. Fix it.

Fixes: 865b50fe

 ("crypto: qat - add fw_counters debugfs file")
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>