Don't free(sc) before returning an error from probe, it does not "belong"

to us, subr_bus.c will free it.  This bug (panic: freeing already free)
was exposed by kern/subr_bus.c rev 1.54

Not explicitly approved by: jkh (but this is a showstopper and fallout of
the above approved change)

sys/dev/atkbdc/psm.c

@@ -765,7 +765,6 @@ doopen(int unit, int command_byte)
 				--verbose;   				\
                             kbdc_set_device_mask(sc->kbdc, mask);	\
 			    kbdc_lock(sc->kbdc, FALSE);			\
- 	                    free(sc, M_DEVBUF);                         \
 			    return (v);	     				\
 			}
 

sys/isa/psm.c

@@ -765,7 +765,6 @@ doopen(int unit, int command_byte)
 				--verbose;   				\
                             kbdc_set_device_mask(sc->kbdc, mask);	\
 			    kbdc_lock(sc->kbdc, FALSE);			\
- 	                    free(sc, M_DEVBUF);                         \
 			    return (v);	     				\
 			}