MAINTAINERS: make linux-aspeed list remarks consistent

Commit f15a3ea8

 ("MAINTAINERS: Add ASPEED BMC GFX DRM driver entry")
does not mention that linux-aspeed@lists.ozlabs.org is moderated for
non-subscribers, but the other three entries for
linux-aspeed@lists.ozlabs.org do.

By 'majority vote' among entries, let us assume it was just missed here and
adjust it to be consistent with others.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200912183334.22683-1-lukas.bulwahn@gmail.com