Dumping the dtb from new versions of QEMU warns that sv57 is an
undocumented mmu-type. The kernel has supported sv57 for about a year,
so bring it into the fold.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230424-rival-habitual-478567c516f0@spud


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>