MAINTAINERS: Add entry for Rust cpumask API

Update the MAINTAINERS file to include the Rust abstractions for cpumask
API.

Yury has indicated that he does not wish to maintain the Rust code but
would like to be listed as a reviewer.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Yury Norov <yury.norov@gmail.com>

Author: vireshk

MAINTAINERS

@@ -6237,6 +6237,12 @@ L:	linux-riscv@lists.infradead.org
 S:	Maintained
 F:	drivers/cpuidle/cpuidle-riscv-sbi.c
 
+CPUMASK API [RUST]
+M:	Viresh Kumar <viresh.kumar@linaro.org>
+R:	Yury Norov <yury.norov@gmail.com>
+S:	Maintained
+F:	rust/kernel/cpumask.rs
+
 CRAMFS FILESYSTEM
 M:	Nicolas Pitre <nico@fluxnic.net>
 S:	Maintained