Fix Compatibility Module io wrapping (#2355) (#2358)

The new reflection based IO autowrapping for compatibility mode Modules
would previously throw a NullPointerExceptions if any hardware were
constructed in the Module before "val io" was initialized. The logic is
now more robust for this case.

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>
(cherry picked from commit 50e6099f

)

Co-authored-by: Jack Koenig <koenig@sifive.com>