Merge tag 'u-boot-rockchip-20190819' of https://gitlab.denx.de/u-boot/custodians/u-boot-rockchip

- Add ROC-RK3399-PC board support
- Move CONFIG_SPI_FLASH_GIGADEVICE and CONFIG_CMD_USB_MASS_STORAGE to
  Kconfig
- using SYSRESET_POWER_OFF for poweroff
  (Note that patch for rk8xx pmic is droped for it can not pass Travis
  build)
- fix ofnode_get_name() assert