U-Boot configuration changes:
- Enable "sbi" command.
- Enable SBI reset and poweroff from U-Boot prompt.
- Set max CPUs on QEMU to 32 for now.
- Enable relocation and use firmware FDT/DTB (i.e. generated by QEMU)
for QEMU.
Signed-off-by: David Abdurachmanov <davidlt@rivosinc.com>
