MAINTAINERS: add RISC-V's patchwork

The RISC-V patchwork instance on kernel.org has had some necromancy
performed on it & will be used going forward. The statuses that are
intended to be used are:
- New: No action has been taken yet
- Under Review: The maintainer is waiting for review comments from others
- Changes Requested: Either the maintainer or a reviewer requested
  changes in the patch. The patch author is expected to submit a new
  version
- Superseded: There's a new version of the patch available
- Not Applicable: The patch is not intended for the RISC-V tree
- Accepted: The patch has been applied
- Rejected: The patch has been rejected, with reasons stated in an
  email

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221011160744.2167025-1-conor@kernel.org/
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: ConchuOD

MAINTAINERS

@@ -17634,6 +17634,7 @@ M:	Palmer Dabbelt <palmer@dabbelt.com>
 M:	Albert Ou <aou@eecs.berkeley.edu>
 L:	linux-riscv@lists.infradead.org
 S:	Supported
+Q:	https://patchwork.kernel.org/project/linux-riscv/list/
 P:	Documentation/riscv/patch-acceptance.rst
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git
 F:	arch/riscv/