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

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

- Fix SiFive HiFive Unleashed board booting failure problem.
- Enable SiFive fu540 PWM driver.
- Support SiFive fu540: SPI boot.
- Update OpenSBI used for RISC-V CI testing.
- Revert "riscv: Allow use of reset drivers".
- Revert "Revert "riscv: sifive: fu540: Add gpio-restart support"".
- sysreset: syscon:
        - Don't assume default value for offset and mask property.
        - Support value property.
- qemu: Add syscon reboot and poweroff support.
- Fix SIFIVE debug serial dependency.
- Fix linking error when building u-boot-spl with no SMP support.
- AE350 use fdtdec_get_addr_size_auto_noparent to parse smc reg.
- Make memory node available to SPL in hifive-unleashed-a00-u-boot.dtsi
- SiFive fu540 avoid using hardcoded ram base and size.