kconfig: use buildin function to get app version

Author: redchenjs

main/Kconfig.projbuild

@@ -276,10 +276,4 @@ config ENABLE_AUDIO_PROMPT
         Select this to enable Audio Prompt.
 endmenu
 
-config FIRMWARE_VERSION
-    string "Firmware Version"
-    default "v3.2.1"
-    help
-        Set Firmware Version.
-
 endmenu

main/src/os/firmware.c

@@ -8,12 +8,13 @@
 #include <string.h>
 
 #include "esp_log.h"
+#include "esp_ota_ops.h"
 
 #define TAG "os_firmware"
 
-const char *version = CONFIG_FIRMWARE_VERSION;
-
 const char *os_firmware_get_version(void)
 {
-    return version;
+    const esp_app_desc_t *app_desc = esp_ota_get_app_description();
+
+    return (const char *)app_desc->version;
 }