test: Run all the fpi-device tests with the dynamically loaded TOD driver

We can ensure better that it works as expected repeating all the device
tests for it too.

The nice part is that we can just do this by re-defininig its GType as
the gtype of the loaded driver.

tests/test-utils-tod.h

@@ -21,3 +21,5 @@
 #include "test-utils.h"
 
 FptContext * fpt_context_new_with_fake_dev (void);
+
+FptContext * fpt_context_fake_dev_default (void);