selftests/net: Add log.txt and tools to .gitignore

Update .gitignore to untrack tools directory and log.txt. "tools" is
generated in "selftests/net/Makefile" and log.txt is generated in
"selftests/net/gro.sh" when executing run_all_tests.
Signed-off-by: Anh Tuan Phan <tuananhlfc@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/.gitignore

@@ -15,6 +15,7 @@ ip_local_port_range
 ipsec
 ipv6_flowlabel
 ipv6_flowlabel_mgr
+log.txt
 msg_zerocopy
 nettest
 psock_fanout
@@ -45,6 +46,7 @@ test_unix_oob
 timestamping
 tls
 toeplitz
+tools
 tun
 txring_overwrite
 txtimestamp