selftests/net: skip psock_tpacket test if KALLSYMS was not enabled

BugLink: https://bugs.launchpad.net/bugs/1812176

The psock_tpacket test will need to access /proc/kallsyms, this would
require the kernel config CONFIG_KALLSYMS to be enabled first.

Apart from adding CONFIG_KALLSYMS to the net/config file here, check the
file existence to determine if we can run this test will be helpful to
avoid a false-positive test result when testing it directly with the
following commad against a kernel that have CONFIG_KALLSYMS disabled:
    make -C tools/testing/selftests TARGETS=net run_tests
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
(backported from commit ff95bf28)
[PHLin: skip changes in config file]
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

tools/testing/selftests/net/run_afpackettests

@@ -20,11 +20,15 @@ fi
 echo "--------------------"
 echo "running psock_tpacket test"
 echo "--------------------"
-./in_netns.sh ./psock_tpacket
-if [ $? -ne 0 ]; then
-	echo "[FAIL]"
-	ret=1
+if [ -f /proc/kallsyms ]; then
+	./in_netns.sh ./psock_tpacket
+	if [ $? -ne 0 ]; then
+		echo "[FAIL]"
+		ret=1
+	else
+		echo "[PASS]"
+	fi
 else
-	echo "[PASS]"
+	echo "[SKIP] CONFIG_KALLSYMS not enabled"
 fi
 exit $ret