ice: remove rx_len_errors statistic

It was found that this statistic is incorrectly
reported by HW and thus, useless.

As RX length error statistics are shown to the
end user when requested, the values reported
are misleading.

Thus, that value is no longer reported and
doesn't count anymore when adding all rx errors.

Signed-off-by: Jan Sokolowski <jan.sokolowski@intel.com>
Reviewed-by: Mateusz Polchlopek <mateusz.polchlopek@intel.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>