staging: unisys: visornic: Fix receive bytes statistics

The receive byte statistics was wrong in /proc/net/dev.

Move the collection of statistics after the proper amount
of bytes has been calculated and make sure you add it to
rx_bytes instead of just replacing it.

Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>