ARM: dts: imx25: add alias for pwm nodes

This, together with the corresponding patch to pwm-imx.c,  allows to order the
pwm devices correctly.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx25.dtsi

@@ -24,6 +24,10 @@
 		i2c2 = &i2c3;
 		mmc0 = &esdhc1;
 		mmc1 = &esdhc2;
+		pwm0 = &pwm1;
+		pwm1 = &pwm2;
+		pwm2 = &pwm3;
+		pwm3 = &pwm4;
 		serial0 = &uart1;
 		serial1 = &uart2;
 		serial2 = &uart3;