ix.4: Document E610 debug dump
Explain how to collect E610 device debug dump data with sysctl for
troubleshooting with Intel Customer Support.
Fixes: 2170400142b9 (Add support for debug dump)
Reviewed by: bcr, erj (previous version), ziaee
Signed-off-by: Yogesh Bhosale <yogesh.bhosale@intel.com>
Differential Revision: https://reviews.freebsd.org/D52990