Driver allocates replacement buffers before-hand to make
sure whenever an aggregation begins there would be a replacement
for the Rx buffers, as we can't release the buffer until
aggregation is terminated and driver logic assumes the Rx rings
are always full.

For every other Rx page that's being allocated [I.e., regular]
the page is being completely mapped while for the replacement
buffers only the first portion of the page is being mapped.
This means that:
  a. Once replacement buffer replenishes the regular Rx ring,
assuming there's more than a single packet on page we'd post unmapped
memory toward HW [assuming mapping is actually done in granularity
smaller than page].
  b. Unmaps are being done for the entire page, which is incorrect.

Fixes: 55482edc

 ("qede: Add slowpath/fastpath support and enable hardware GRO")
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>