e1000e: Fix tx/rx counters

e1000e: Fix tx/rx counters

The bytes and packets counter registers are cleared on read.

Copying the "total counter" registers to the "good counter" registers has
side effects.
If the "total" register is never read by the OS, it only gets incremented.
This leads to exponential growth of the "good" register.

This commit increments the counters individually to avoid this.

Signed-off-by: Timothée Cocault <timothee.cocault@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>