ARM: imx_v6_v7_defconfig: Set THERMAL_WRITABLE_TRIPS=y for testing

Setting trip points is supported by the imx thermal driver and it is
useful to be able to test this without adjusting config.
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -207,6 +207,7 @@ CONFIG_POWER_SUPPLY=y
 CONFIG_SENSORS_GPIO_FAN=y
 CONFIG_SENSORS_IIO_HWMON=y
 CONFIG_THERMAL=y
+CONFIG_THERMAL_WRITABLE_TRIPS=y
 CONFIG_CPU_THERMAL=y
 CONFIG_IMX_THERMAL=y
 CONFIG_WATCHDOG=y