libata: replace tf_read with qc_fill_rtf for non-SFF drivers

Now that all SFF stuff is separated out of core layer, core layer
doesn't call ops->tf_read directly.  It gets called only via
ops->qc_fill_rtf() for non-SFF drivers.  This patch directly
implements private ops->qc_fill_rtf() for non-SFF controllers and kill
ops->tf_read().

This is much cleaner for non-SFF controllers as some of them have to
cache SFF register values in private data structure and report the
cached values via ops->tf_read().  Also, ops->tf_read() gets nasty for
controllers which don't have clear notion of TF registers when
operation is not in progress.

As this change makes default ops->qc_fill_rtf unnecessary, move
ata_sff_qc_fill_rtf() form ata_base_port_ops to ata_sff_port_ops where
it belongs.

Signed-off-by: Tejun Heo <htejun@gmail.com>

drivers/ata/libata-sff.c

@@ -44,6 +44,7 @@ const struct ata_port_operations ata_sff_port_ops = {
 
 	.qc_prep		= ata_sff_qc_prep,
 	.qc_issue		= ata_sff_qc_issue,
+	.qc_fill_rtf		= ata_sff_qc_fill_rtf,
 
 	.freeze			= ata_sff_freeze,
 	.thaw			= ata_sff_thaw,