thermal: fix mtk_thermal build dependency

Fix build errors when MTK_THERMAL=y and NVMEM=m by preventing that
Kconfig combination.

drivers/built-in.o: In function `mtk_thermal_probe':
mtk_thermal.c:(.text+0xffa8f): undefined reference to `nvmem_cell_get'
mtk_thermal.c:(.text+0xffabe): undefined reference to `nvmem_cell_read'
mtk_thermal.c:(.text+0xffac9): undefined reference to `nvmem_cell_put'

Signed-off-by: Randy Dunlap <[email protected]>
Cc: Zhang Rui <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: <[email protected]>
Cc: Sascha Hauer <[email protected]>
Cc: Hanyi Wu <[email protected]>
Signed-off-by: Eduardo Valentin <[email protected]>

Author: rddunlap

drivers/thermal/Kconfig

@@ -376,6 +376,7 @@ config MTK_THERMAL
 	tristate "Temperature sensor driver for mediatek SoCs"
 	depends on ARCH_MEDIATEK || COMPILE_TEST
 	depends on HAS_IOMEM
+	depends on NVMEM || NVMEM=n
 	default y
 	help
 	  Enable this option if you want to have support for thermal management