net: Remove unneeded version.h includes from drivers/net/

It was pointed out by 'make versioncheck' that some includes of
linux/version.h are not needed in drivers/net/.
This patch removes them.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: David S. Miller <davem@davemloft.net>