drivers/net: Kconfig & Makefile cleanup

The is does a general cleanup of the drivers/net/ Kconfig and
Makefile.  This patch create a "core" option and places all
the networking core drivers into this option (default is yes
for this option).  In addition, it alphabitizes the Kconfig
driver options.

As a side cleanup, found that the arcnet, token ring, and PHY
Kconfig options were a tri-state option and should have been
a bool option.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>