Maintainers: Drop Masami as reviewer

Masami's linaro email started bouncing, and he has indicated that he is
no longer available to review SynQuacer patches. So drop him from the
list.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@google.com>