ARM: dts: am335x-baltos: change nand-xfer-type

Use "prefetch-dma" instead of "polled".

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Message-Id: <20220705122355.14854-1-yegorslists@googlemail.com>
Acked-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>