Palmer, with Konstantin's gracious help, set up a shared kernel.org
git tree for arch/riscv patches going forward.  Change the MAINTAINERS
file accordingly.
Signed-off-by: NPaul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Reviewed-by: NPalmer Dabbelt <palmer@sifive.com>