ARM: dts: omap3-igep0020: use standard constant for IRQ flags

Commit 840ef8b7 ("ARM: dt: add header to define IRQ flags") added
constants for IRQ edge/level triggered types so use it instead of
a magic number to enhance the DT readability.
Signed-off-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: NBenoit Cousson <bcousson@baylibre.com>

arch/arm/boot/dts/omap3-igep0020.dts

@@ -199,7 +199,7 @@
 		gpmc,cycle2cycle-diffcsen;
 
 		interrupt-parent = <&gpio6>;
-		interrupts = <16 8>;
+		interrupts = <16 IRQ_TYPE_LEVEL_LOW>;
 		vmmc-supply = <&vddvario>;
 		vmmc_aux-supply = <&vdd33a>;
 		reg-io-width = <4>;