patman: Use the full commit hash for 'git checkout'

Even with the initial 8 characeters of the hash we will sometimes get a
collision. Use the full hash.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/patchstream.py b/tools/patman/patchstream.py
index d630157..da04883 100644
--- a/tools/patman/patchstream.py
+++ b/tools/patman/patchstream.py
@@ -248,8 +248,7 @@
         # Detect the start of a new commit
         elif commit_match:
             self.CloseCommit()
-            # TODO: We should store the whole hash, and just display a subset
-            self.commit = commit.Commit(commit_match.group(1)[:8])
+            self.commit = commit.Commit(commit_match.group(1))
 
         # Detect tags in the commit message
         elif tag_match: