RISC-V: Don't set cacheinfo.{physical_line_partition,attributes}

These are just hard coded in the RISC-V port, which doesn't make any
sense.  We should probably be setting these from device tree entries
when they exist, but for now I think it's saner to just leave them all
as their default values.

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