kbd drivers: use kbdd_* indirection for diag invocation

These invocations were directly calling enkbd_diag(), rather than
indirection back through kbdd_diag/kbdsw. While they're functionally
equivent, invoking kbdd_diag where feasible (i.e. not in a diag
implementation) makes it easier to visually identify locking needs in these
other drivers.