Merge tag 'mips-pull-2020-06-29' of https://gitlab.denx.de/u-boot/custodians/u-boot-mips into next

- net: pcnet: cleanup and add DM support
- Makefile: add rule to build an endian-swapped U-Boot image
  used by MIPS Malta EL variants
- CI: add Qemu tests for MIPS Malta