add internal patch marker (#173)

all internal patches will be added below the marker. This eases
internal patch management when public patches change

Signed-off-by: Guohan Lu <lguohan@gmail.com>

patch/series

@@ -75,3 +75,9 @@ driver-ixgbe-external-phy.patch
 0019-mlxsw-i2c-Allow-flexible-setting-of-I2C-transactions.patch
 0020-mlxsw-core-Set-different-thermal-polling-time-based.patch
 0021-platform-x86-mlx-platform-Remove-PSU-EEPROM-configur.patch
+############################################################
+#
+# Internal patches will be added below (placeholder)
+# Do not add any public patch below this marker
+#
+############################################################