mv643xx_eth: pass port identifier to register accessors

Pass a struct mv643xx_private * to the register accessor functions,
as a preparation for having multiple mv643xx_eth silicon blocks.

(Since this causes some 80 column straddling, and the mv_ prefix
is useless anyway, rename mv_read to rdl and mv_write to wrl to
compensate.)

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Reviewed-by: Tzachi Perelstein <tzachi@marvell.com>
Signed-off-by: Dale Farnsworth <dale@farnsworth.org>