mv643xx_eth: kill superfluous comments

Half of the functions in the mv643xx_eth driver are prefixed by
useless and baroque comment blocks on _what_ those functions do (which
is obvious from the code itself) rather than why, and there's no point
in keeping those comments around.
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Acked-by: Dale Farnsworth <dale@farnsworth.org>