kunit: test: Drop CONFIG_MODULE ifdeffery

The function stubs exposed by module.h allow the code to compile properly
without the ifdeffery. The generated object code stays the same, as the
compiler can optimize away all the dead code.
As the code is still typechecked developer errors can be detected faster.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: David Gow <davidgow@google.com>
Reviewed-by: Daniel Gomez <da.gomez@samsung.com>
Link: https://lore.kernel.org/r/20250711-kunit-ifdef-modules-v2-3-39443decb1f8@linutronix.de


Signed-off-by: Daniel Gomez <da.gomez@samsung.com>