mv643xx_eth: use 'mv643xx_eth_' prefix consistently

A bunch of places in the mv643xx_eth driver use the 'mv643xx_'
prefix.  Since the mv643xx is a chip that includes more than just
ethernet, this patch makes all those places use either no prefix
(for some internal-use-only functions), or the full 'mv643xx_eth_'
prefix.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Acked-by: Dale Farnsworth <dale@farnsworth.org>