Return the diag buffer release command with -EINVAL status if the buffer is
already released.

Link: https://lore.kernel.org/r/1568379890-18347-10-git-send-email-sreekanth.reddy@broadcom.comSigned-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>