ARM: dts: imx6sl: correct PWM ipg clock source

From i.MX6SL Reference Manual, the PWMx's ipg clock
for registers access is from perclk, correct them.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6sl.dtsi

@@ -338,7 +338,7 @@ pwm1: pwm@2080000 {
 				compatible = "fsl,imx6sl-pwm", "fsl,imx27-pwm";
 				reg = <0x02080000 0x4000>;
 				interrupts = <0 83 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&clks IMX6SL_CLK_PWM1>,
+				clocks = <&clks IMX6SL_CLK_PERCLK>,
 					 <&clks IMX6SL_CLK_PWM1>;
 				clock-names = "ipg", "per";
 			};
@@ -348,7 +348,7 @@ pwm2: pwm@2084000 {
 				compatible = "fsl,imx6sl-pwm", "fsl,imx27-pwm";
 				reg = <0x02084000 0x4000>;
 				interrupts = <0 84 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&clks IMX6SL_CLK_PWM2>,
+				clocks = <&clks IMX6SL_CLK_PERCLK>,
 					 <&clks IMX6SL_CLK_PWM2>;
 				clock-names = "ipg", "per";
 			};
@@ -358,7 +358,7 @@ pwm3: pwm@2088000 {
 				compatible = "fsl,imx6sl-pwm", "fsl,imx27-pwm";
 				reg = <0x02088000 0x4000>;
 				interrupts = <0 85 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&clks IMX6SL_CLK_PWM3>,
+				clocks = <&clks IMX6SL_CLK_PERCLK>,
 					 <&clks IMX6SL_CLK_PWM3>;
 				clock-names = "ipg", "per";
 			};
@@ -368,7 +368,7 @@ pwm4: pwm@208c000 {
 				compatible = "fsl,imx6sl-pwm", "fsl,imx27-pwm";
 				reg = <0x0208c000 0x4000>;
 				interrupts = <0 86 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&clks IMX6SL_CLK_PWM4>,
+				clocks = <&clks IMX6SL_CLK_PERCLK>,
 					 <&clks IMX6SL_CLK_PWM4>;
 				clock-names = "ipg", "per";
 			};