gitlint: allow Fixes to exceed line length

The Kernel convention for "Fixes" directives is as follows[1]:

```
If your patch fixes a bug in a specific commit, e.g. you found an issue
using git bisect, please use the ‘Fixes:’ tag with the first 12
characters of the SHA-1 ID, and the one line summary. Do not split the
tag across multiple lines, tags are exempt from the “wrap at 75
columns” rule in order to simplify parsing scripts.
```

Some repositories follow this convention, so allow it in the commit
message by ignoring lines that start with "Fixes:".

[1]: https://docs.kernel.org/process/submitting-patches.html

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I81aa98663d421ff670f09dd048d12a48c32ce3c5
diff --git a/config/gitlint/block_comment.py b/config/gitlint/block_comment.py
index d5cc3f8..452aa8c 100644
--- a/config/gitlint/block_comment.py
+++ b/config/gitlint/block_comment.py
@@ -48,6 +48,10 @@
             if line.startswith("Signed-off-by:"):
                 continue
 
+            # allow Fixes
+            if line.startswith("Fixes:"):
+                continue
+
             max_length = self.options["line-length"].value
             if len(line) > max_length:
                 return [