Revert "mv643xx_eth: use longer DMA bursts".

This reverts commit cd4ccf76.

On the Pegasos board, we can't do DMA burst that are longer than
one cache line.  For now, go back to using 32 byte DMA bursts for
all mv643xx_eth platforms -- we can switch the ARM-based platforms
back to doing long 128 byte bursts in the next development cycle.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Reported-by: Alan Curry <pacman@kosh.dhis.org>
Reported-by: Gabriel Paubert <paubert@iram.es>
Signed-off-by: David S. Miller <davem@davemloft.net>