fsi: occ: Fix checksum failure mode

Change the checksum errno to something different than the errno
used for a bad SBE message. In addition, don't set the user's
response length to the data length in this case, since it's not
SBE FFDC.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20220426154956.27205-2-eajames@linux.ibm.com


Signed-off-by: Joel Stanley <joel@jms.id.au>