net: eepro100: Split common parts of non-DM functions out

Split the common code from the non-DM code, so it can be reused by
the DM code later. As always, the recv() function had to be split
into the actual receiving part and free_pkt part to fit with the
DM.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>