chore: fix warnings

src/libs/fsdrv/lv_fs_posix.c

@@ -188,6 +188,8 @@ static lv_fs_res_t fs_seek(lv_fs_drv_t * drv, void * file_p, uint32_t pos, lv_fs
         case LV_FS_SEEK_END:
             w = SEEK_END;
             break;
+        default:
+            return LV_FS_RES_INV_PARAM;
     }
 
     off_t offset = lseek((lv_uintptr_t)file_p, pos, w);

src/libs/fsdrv/lv_fs_stdio.c

@@ -178,7 +178,22 @@ static lv_fs_res_t fs_write(lv_fs_drv_t * drv, void * file_p, const void * buf,
 static lv_fs_res_t fs_seek(lv_fs_drv_t * drv, void * file_p, uint32_t pos, lv_fs_whence_t whence)
 {
     LV_UNUSED(drv);
-    fseek(file_p, pos, whence);
+    int w;
+    switch(whence) {
+        case LV_FS_SEEK_SET:
+            w = SEEK_SET;
+            break;
+        case LV_FS_SEEK_CUR:
+            w = SEEK_CUR;
+            break;
+        case LV_FS_SEEK_END:
+            w = SEEK_END;
+            break;
+        default:
+            return LV_FS_RES_INV_PARAM;
+    }
+
+    fseek(file_p, pos, w);
     return LV_FS_RES_OK;
 }