[libata] ensure ->tf_read() hook reads Status and Error registers

We want ->tf_read() to get a complete snapshot of all taskfile
registers, without requiring the callers to manually call
ata_chk_status() and ata_chk_err() themselves.

This also fixes a minor bug in sata_vsc where the lower bits of the
feature register were incorrectly placed in the HOB (high order bits)
portion of struct ata_taskfile.
diff --git a/drivers/scsi/pdc_adma.c b/drivers/scsi/pdc_adma.c
index 7999817..af99feb 100644
--- a/drivers/scsi/pdc_adma.c
+++ b/drivers/scsi/pdc_adma.c
@@ -490,7 +490,7 @@
 			if (qc && (!(qc->tf.ctl & ATA_NIEN))) {
 
 				/* check main status, clearing INTRQ */
-				u8 status = ata_chk_status(ap);
+				u8 status = ata_check_status(ap);
 				if ((status & ATA_BUSY))
 					continue;
 				DPRINTK("ata%u: protocol %d (dev_stat 0x%X)\n",