net: change Exar/Neterion menu items to be alphabetical

Neterion was standalone for several years, then acquired by Exar and
shutdown in 11 months without ever making any new Exar branded adapters.
Users would probably think of them as Neterion and not Exar (as there
have been no follow-on adapters and the vast majority ever sold were
under the Neterion name).

6c541b45 ("net: ethernet: Sort Kconfig sourcing alphabetically")
sorted Kconfig sourcing based on directory names, but in a couple cases,
the menu item text is quite different from the directory name and is not
sorted correctly:

  drivers/net/ethernet/neterion/Kconfig    => "Exar devices"

To address that and clear up any confusion about the name, "Exar" was
changed to "Neterion (Exar)" and the relevant entries in the Makefile
and Kconfig were reordered to match the alphabetical organization.

Inspired-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: David S. Miller <davem@davemloft.net>