net: ethernet: ibm: ehea: Remove duplicate object from Makefile

In the Makefile, ehea_phyp.o is included twice in the list of
object files compile into ehea.o.

This change removes one instance.

Signed-off-by: Andreas Ruprecht <rupran@einserver.de>
Signed-off-by: David S. Miller <davem@davemloft.net>