cxlflash: a couple off by one bugs

The "> MAX_CONTEXT" should be ">= MAX_CONTEXT".  Otherwise we go one
step beyond the end of the cfg->ctx_tbl[] array.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Manoj Kumar <manoj@linux.vnet.ibm.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>