fix(rt-thread): use ARCH_CPU_BIG_ENDIAN to replace RT_USING_BIG_ENDIAN
* COMPILER SETTINGS
*====================*/
-#ifdef RT_USING_BIG_ENDIAN
+#ifdef ARCH_CPU_BIG_ENDIAN
# define LV_BIG_ENDIAN_SYSTEM 1
#else
# define LV_BIG_ENDIAN_SYSTEM 0
