Fix compile errors on ia64 in dagetcapacity. Set block_len and maxsector

to 0 initially.  It seems that the ia64 backend isn't as "smart" as the
i386 backend, which realized that those variables were only set or used
when error == 0, and thus were not used uninitialized.

sys/cam/scsi/scsi_da.c

@@ -1785,6 +1785,8 @@ dagetcapacity(struct cam_periph *periph)
 	int error;
 
 	softc = (struct da_softc *)periph->softc;
+	block_len = 0;
+	maxsector = 0;
 	error = 0;
 
 	/* Do a read capacity */