Merge https://gitlab.denx.de/u-boot/custodians/u-boot-riscv

- Adds few DT related fixes required for Linux EFI stub to work on
  RISC-V.
- Makes SBI v0.2 the default SBI version to work with OpenSBI v0.7.
- Revert "riscv: qemu: clear kernel-start/-end in device tree as
  workaround for BBL"
- Remove unnecessary CONFIG_IS_ENABLED().