[SCSI] libsas: remove spurious sata control register read/write

Originally, libata required the illusion that it could access the sata
control register.  Now, however, it can run perfectly well without
them, so remove the dummy routines from libsas which tried to emulate
them (but only ended up causing confusion).

Signed-off-by: James Bottomley <James.Bottomley@suse.de>