ARM: dts: am437x: Fix GPMC dma properties

ARM: dts: am437x: Fix GPMC dma properties

commit 883cbc901b570625f54250a37b008d3635f1fbda upstream.

This patch updates the GPMC's DT DMA property to reflect the updated eDMA
bindings.

Fixes: cce1ee000187 ("ARM: DTS: am437x: Use the new DT bindings for the eDMA3")
Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>