net: Move CONFIG_RTL8139 to Kconfig

Introduce CONFIG_RTL8139 in Kconfig and move over boards' defconfig
to use that.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
[trini: Fixup MPC8641HPCN* and r2dplus configs]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index bc2f51d..3ac6b66 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -102,6 +102,12 @@
 	  This MAC is present in Intel Platform Controller Hub EG20T. It
 	  supports 10/100/1000 Mbps operation.
 
+config RTL8139
+	bool "Realtek 8139 series Ethernet controller driver"
+	help
+	  This driver supports Realtek 8139 series fast ethernet family of
+	  PCI chipsets/adapters.
+
 config XILINX_AXIEMAC
 	depends on DM_ETH && (MICROBLAZE || ARCH_ZYNQ || ARCH_ZYNQMP)
 	select PHYLIB