arm-bsp/linux-linaro-arm: enable Realtek R8169 eth adapter driver for N1SDP

By default kernel defconfig is not enabled to support Realtek adapter driver
required to get ethernet working on N1SDP. This patch enables the CONFIG_R8169
to add the support.

Issue-Id: PLATFORMS-3134
Change-Id: I218ca8e0011db7f02329e103c1dea1350ccc3c28
Signed-off-by: Khasim Syed Mohammed <khasim.mohammed@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm-bsp/recipes-kernel/linux/linux-linaro-arm-5.4/n1sdp/enable-realtek-R8169.cfg

@@ -0,0 +1,2 @@
+# Enable Realtek Gigabit Ethernet adapter
+CONFIG_R8169=y

meta-arm-bsp/recipes-kernel/linux/linux-linaro-arm_5.4.bbappend

@@ -11,6 +11,7 @@ SRC_URI_append_n1sdp = " \
     file://0002-pci_quirk-add-acs-override-for-PCI-devices.patch \
     file://0003-pcie-Add-quirk-for-the-Arm-Neoverse-N1SDP-platform.patch \
     file://0004-n1sdp-update-n1sdp-pci-quirk-for-SR-IOV-support.patch \
+    file://enable-realtek-R8169.cfg \
     "
 
 # Referring to commit TAG N1SDP-2020.03.26