net: Allow FIXED_PHY to be modular.

Otherwise we get things like:

warning: (NET_DSA_BCM_SF2 && BCMGENET && SYSTEMPORT) selects FIXED_PHY which has unmet direct dependencies (NETDEVICES && PHYLIB=y)

In order to make this work we have to rename fixed.c to fixed_phy.c
because the regulator drivers already have a module named "fixed.o".

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc drivers/net/phy/Kconfig
Simple merge

diff --cc drivers/net/phy/Makefile
Simple merge

diff --cc drivers/net/phy/fixed_phy.c
Simple merge

diff --cc include/linux/phy_fixed.h
Simple merge