Fix lfs_file_seek doesn't update cache properties correctly in readonly mode. Invalidate cache to fix it.

lfs.c

@@ -2730,14 +2730,18 @@ static int lfs_file_outline(lfs_t *lfs, lfs_file_t *file) {
 }
 #endif
 
-#ifndef LFS_READONLY
-static int lfs_file_flush(lfs_t *lfs, lfs_file_t *file) {
+static void lfs_file_invalidate_reading_flag(lfs_t *lfs, lfs_file_t *file) {
     if (file->flags & LFS_F_READING) {
         if (!(file->flags & LFS_F_INLINE)) {
             lfs_cache_drop(lfs, &file->cache);
         }
         file->flags &= ~LFS_F_READING;
     }
+}
+
+#ifndef LFS_READONLY
+static int lfs_file_flush(lfs_t *lfs, lfs_file_t *file) {
+    lfs_file_invalidate_reading_flag(lfs, file);
 
     if (file->flags & LFS_F_WRITING) {
         lfs_off_t pos = file->pos;
@@ -3087,6 +3091,10 @@ static lfs_soff_t lfs_file_rawseek(lfs_t *lfs, lfs_file_t *file,
     if (err) {
         return err;
     }
+#else
+    // Seek doesn't update cache parameters properly.
+    // It has to be invalidated otherwise next read will return incorrect values.
+    lfs_file_invalidate_reading_flag(lfs,file);
 #endif
 
     // update pos