Ensure all source code end with one and only one newline

by this command:
git ls-files -z | while IFS= read -rd '' f; do tail -c1 < "$f" | read -r _ || echo >> "$f"; done

fs/littlefs/Make.defs

@@ -52,4 +52,4 @@ CSRCS += lfs.c lfs_util.c lfs_vfs.c
 DEPPATH += --dep-path littlefs
 VPATH += :littlefs
 
-endif
+endif

fs/spiffs/docs/TODO

@@ -12,4 +12,4 @@ SPIFFS2 thoughts
 
 * Steal one page, use as a bit parity page. When starting an fs modification operation, write one bit
   as zero. When ending, write another bit as zero. On mount, if number of zeroes in page is uneven, a
-  check is automatically run.
+  check is automatically run.

fs/spiffs/src/spiffs_check.c

@@ -2216,4 +2216,4 @@ int spiffs_dump(FAR struct spiffs_s *fs)
                    (long)(ndata_pages * data_pgsize));
   return OK;
 }
-#endif
+#endif

fs/userfs/userfs.h

@@ -49,4 +49,4 @@
  ****************************************************************************/
 
 #endif /* CONFIG_FS_USERFS */
-#endif /* __FS_USERFS_USERFS_H */
+#endif /* __FS_USERFS_USERFS_H */