Set CONFIG_HAS_CAP_ENTER to support posix file api for freertos (#3041)

Since there is no so rich api in freertos like embedded system, simply set
CONFIG_HAS_CAP_ENTER to 1 to support posix file api for freertos.
Test file api in wasm app pass.

core/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/ssp_config.h

@@ -34,7 +34,7 @@
 #define CONFIG_HAS_GETRANDOM 0
 #endif
 
-#if defined(__CloudABI__)
+#if defined(__CloudABI__) || defined(BH_PLATFORM_FREERTOS)
 #define CONFIG_HAS_CAP_ENTER 1
 #else
 #define CONFIG_HAS_CAP_ENTER 0