ARM: dts: imx: update snvs-poweroff mask

Make the syscon-poweroff driver change only the shutdown bits on the
SNVS_LP control register.

This change fixes an issue with the RTC wakeup alarm, that was
previously disabled during power off.
Signed-off-by: NGuy Shapiro <guy.shapiro@mobi-wize.com>
Reviewed-by: NMarcin Niestroj <m.niestroj@grinn-global.com>
Reviewed-by: NFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl.dtsi

@@ -769,6 +769,7 @@
 					compatible = "syscon-poweroff";
 					regmap = <&snvs>;
 					offset = <0x38>;
+					value = <0x60>;
 					mask = <0x60>;
 					status = "disabled";
 				};

arch/arm/boot/dts/imx6sl.dtsi

@@ -655,6 +655,7 @@
 					compatible = "syscon-poweroff";
 					regmap = <&snvs>;
 					offset = <0x38>;
+					value = <0x60>;
 					mask = <0x60>;
 					status = "disabled";
 				};

arch/arm/boot/dts/imx6sx.dtsi

@@ -710,6 +710,7 @@
 					compatible = "syscon-poweroff";
 					regmap = <&snvs>;
 					offset = <0x38>;
+					value = <0x60>;
 					mask = <0x60>;
 					status = "disabled";
 				};

arch/arm/boot/dts/imx6ul.dtsi

@@ -614,6 +614,7 @@
 					compatible = "syscon-poweroff";
 					regmap = <&snvs>;
 					offset = <0x38>;
+					value = <0x60>;
 					mask = <0x60>;
 					status = "disabled";
 				};

arch/arm/boot/dts/imx7s.dtsi

@@ -540,6 +540,7 @@
 					compatible = "syscon-poweroff";
 					regmap = <&snvs>;
 					offset = <0x38>;
+					value = <0x60>;
 					mask = <0x60>;
 				};