r8169: rename r8169.c to r8169_main.c

In preparation of factoring out firmware handling rename r8169.c to
r8169_main.c.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/Makefile

@@ -6,4 +6,5 @@
 obj-$(CONFIG_8139CP) += 8139cp.o
 obj-$(CONFIG_8139TOO) += 8139too.o
 obj-$(CONFIG_ATP) += atp.o
+r8169-objs += r8169_main.o
 obj-$(CONFIG_R8169) += r8169.o