MAINTAINERS: update maintainership of pxa2xx/pxa3xx

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Acked-by: Russell King <rmk@arm.linux.org.uk>
Acked-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>