clean_header: Don't print extraneous newline char

Don't print an extraneous newline character at the end of the include
file if clean_header.py is used in the non-update mode. This is
necessary to achieve consistent results in the update and non-update
modes.

Running clean_header in the non-update mode and redirecting the output
to a file should have the same result as using the update mode and have
the script write to the file directly.

Change-Id: I6b176c5365840d66e4499bacd205f1fa77302a2b