cmake: dts.cmake: Use SOC_PATH to find soc/dts.fixup

Per arch the path to the SOC dir that we would find dts.fixup varies
between being ${CONFIG_SOC_FAMILY}/${CONFIG_SOC_SERIES} and just
${CONFIG_SOC}.  The ${SOC_PATH} var handles defining this correct so
use it instead when we define DTS_SOC_FIXUP_FILE.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>

Author: galak

cmake/dts.cmake

@@ -89,7 +89,7 @@ if(CONFIG_HAS_DTS)
   if(EXISTS ${DTS_BOARD_FIXUP_FILE})
     set(DTS_BOARD_FIXUP -f ${DTS_BOARD_FIXUP_FILE})
   endif()
-  set_ifndef(DTS_SOC_FIXUP_FILE ${PROJECT_SOURCE_DIR}/arch/${ARCH}/soc/${CONFIG_SOC_FAMILY}/${CONFIG_SOC_SERIES}/dts.fixup)
+  set_ifndef(DTS_SOC_FIXUP_FILE ${PROJECT_SOURCE_DIR}/arch/${ARCH}/soc/${SOC_PATH}/dts.fixup)
   if(EXISTS ${DTS_SOC_FIXUP_FILE})
     set(DTS_SOC_FIXUP -f ${DTS_SOC_FIXUP_FILE})
   endif()