Merge tag 'u-boot-amlogic-20201005' of https://gitlab.denx.de/u-boot/custodians/u-boot-amlogic

- generate unique mac address from SoC serial on S400 board
- Add USB support for GXL and AXG SoCs
- Update Gadget code to use the new GXL and AXG USB glue driver
- Add a VIM3 board support to add dynamic PCIe enable in OS DT
- Fix AXG pinmux with requesting GPIOs
- Add missing GPIOA_18 for AXG pinctrl
- Add Amlogic PWM driver