When adapting the original sources for s390x the JMP_BUF_CNT was
mistakenly halved due to an incorrect assumption of the size of
a unsigned long. They are 8 bytes for the s390x architecture.
Increase JMP_BUF_CNT accordingly.
Authored-by: Don Brady <don.brady@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reported-by: Colin Ian King <canonical.com> Tested-by: Colin Ian King <canonical.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #8992
Closes #9080