Convert CONFIG_IMX_BOOTAUX et al to Kconfig

This converts the following to Kconfig:
   CONFIG_IMX_BOOTAUX
   CONFIG_IMX_THERMAL

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/imx8mq_phanbell_defconfig b/configs/imx8mq_phanbell_defconfig
index 4b7fafe..72ff17f 100644
--- a/configs/imx8mq_phanbell_defconfig
+++ b/configs/imx8mq_phanbell_defconfig
@@ -19,6 +19,7 @@
 CONFIG_SPL_SERIAL=y
 CONFIG_SPL_DRIVERS_MISC=y
 CONFIG_SPL=y
+CONFIG_IMX_BOOTAUX=y
 CONFIG_SYS_LOAD_ADDR=0x40480000
 CONFIG_FIT=y
 CONFIG_FIT_EXTERNAL_OFFSET=0x3000