MAINTAINERS: Add a co-maintainer for RISC-V

Add Leo as co-maintainer for RISC-V.

Signed-off-by: Rick Chen <rick@andestech.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 20092cb..f5c73db 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -981,6 +981,7 @@
 
 RISC-V
 M:	Rick Chen <rick@andestech.com>
+M:	Leo <ycliang@andestech.com>
 S:	Maintained
 T:	git https://source.denx.de/u-boot/custodians/u-boot-riscv.git
 F:	arch/riscv/