We have a bunch of Kconfig symbols which select various IBM_EMAC_*
symbols. These all cause warnings when IBM_EMAC is not selected.
eg.
warning: (PPC_CELL_NATIVE && BLUESTONE && CANYONLANDS && GLACIER &&
EIGER && 440EPX && 440GRX && 440GX && 460SX && 405EX) selects
IBM_EMAC_RGMII which has unmet direct dependencies (NETDEVICES &&
ETHERNET && NET_VENDOR_IBM)
So make them all depend on IBM_EMAC being enabled first.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>