gpiospi: Fix module dependencies.

Approved by: re (cperciva)
MFC after: 3 days
Reviewed by: ray
Differential Revision: https://reviews.freebsd.org/D47570

(cherry picked from commit 79af8f72b3aff993703778423e83320df0953a37)
(cherry picked from commit 3bcbd391dd7e1376ab7ad37e94f5b746abfc0591)