net: Move CONFIG_RTL8169 to Kconfig

Introduce CONFIG_RTL8169 in Kconfig and move over boards' defconfig
to use that.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Stephen Warren <swaren@nvidia.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 3ac6b66..2a229b8 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -108,6 +108,12 @@
 	  This driver supports Realtek 8139 series fast ethernet family of
 	  PCI chipsets/adapters.
 
+config RTL8169
+	bool "Realtek 8169 series Ethernet controller driver"
+	help
+	  This driver supports Realtek 8169 series gigabit ethernet family of
+	  PCI/PCIe chipsets/adapters.
+
 config XILINX_AXIEMAC
 	depends on DM_ETH && (MICROBLAZE || ARCH_ZYNQ || ARCH_ZYNQMP)
 	select PHYLIB