py-smbus: fix module level docs

When you do `pydoc smbus`, you just get the high level description.
There is no automatic display of the classes (like SMBus).  This is
due to the name not being specified quite right in the type.

Contributed by Mike Frysinger.


git-svn-id: http://lm-sensors.org/svn/i2c-tools/trunk@6171 7894878c-1315-0410-8ee3-d5d059ff63e0