Update the RISC-V MAINTAINERS file

Now that we're upstream in Linux we've been able to make some
infrastructure changes so our port works a bit more like other ports.
Specifically:

* We now have a mailing list specific to the RISC-V Linux port, hosted
  at lists.infreadead.org.
* We now have a kernel.org git tree where work on our port is
  coordinated.

This patch changes the RISC-V maintainers entry to reflect these new
bits of infrastructure.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

MAINTAINERS

@@ -11651,8 +11651,8 @@ F:	drivers/mtd/nand/r852.h
 RISC-V ARCHITECTURE
 M:	Palmer Dabbelt <palmer@sifive.com>
 M:	Albert Ou <albert@sifive.com>
-L:	patches@groups.riscv.org
-T:	git https://github.com/riscv/riscv-linux
+L:	linux-riscv@lists.infradead.org
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux.git
 S:	Supported
 F:	arch/riscv/
 K:	riscv