i40e: Remove unused RX realloc stat

After commit 1a557afc ("i40e: Refactor receive routine"),
rx_stats.realloc_count is no longer being incremented, so remove it.

The debugfs string was left, but hardcoded to 0. This is intended to
prevent breaking any existing code / scripts that are parsing debugfs
for i40e.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>