Always use the fallback behaviour for determining the version number

When built from within buildroot the micropython build process detects
that it is inside a git repository and ends up using the buildroot
version number instead of the correct micropython version number.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
---
diff -Naur micropython-v1.4.5-old/py/makeversionhdr.py micropython-v1.4.5/py/makeversionhdr.py
--- micropython-v1.4.5-old/py/makeversionhdr.py    2015-08-12 00:42:30.000000000 +1200
+++ micropython-v1.4.5/py/makeversionhdr.py    2015-09-16 10:21:06.698962836 +1200
@@ -70,9 +70,7 @@
 
 def make_version_header(filename):
     # Get version info using git, with fallback to docs/conf.py
-    info = get_version_info_from_git()
-    if info is None:
-        info = get_version_info_from_docs_conf()
+    info = get_version_info_from_docs_conf()
 
     git_tag, git_hash, ver = info