plip: Move the PLIP driver

Move the Parallel Line Internet Protocol (PLIP) driver into
drivers/net/plip/ and make the necessary Kconfig and Makefile changes.

CC: Niibe Yutaka <gniibe@mri.co.jp>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Alan Cox <alan@linux.intel.com>