uboot-phytec

Merge branch 'master' of https://gitlab.denx.de/u-boot/custodians/u-boot-riscv

- Increase stack size to avoid a stack overflow during distro boot.
- Add hifive-unleashed-a00.dts for SIFIVE FU540.
- Add OF_SEPARATE support for SIFIVE FU540.
- Add SPL support for Andes AX25 AE350.
- Improve U-Boot SPL / OpenSBI smp boot flow for RISC-V.