HW keeps track of RX errors using several counters, each for
specific type of errors. Report RX errors to OS as sum
of all those counters: CRC errors, illegal bytes, checksum,
length, undersize, fragment, oversize and jabber errors.
There is no HW counter for frames with invalid L3/L4 checksums
so add a SW one.
Also add a "rx_errors" sysctl with a copy of netstat IERRORS
counter value to make it easier accessible from scripts.
Reviewed By: erj
Tested By: gowtham.kumar.ks@intel.com
Sponsored By: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D27639