ide: use ->tf_read in ide_read_error()

* Add IDE_TFLAG_IN_FEATURE taskfile flag for reading Feature
  register and handle it in ->tf_read.

* Convert ide_read_error() to use ->tf_read instead of ->INB,
  then uninline and export it.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/include/linux/ide.h b/include/linux/ide.h
index ae93f89..7890768 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -889,6 +889,7 @@
 	IDE_TFLAG_IN_HOB		= IDE_TFLAG_IN_HOB_FEATURE |
 					  IDE_TFLAG_IN_HOB_NSECT |
 					  IDE_TFLAG_IN_HOB_LBA,
+	IDE_TFLAG_IN_FEATURE		= (1 << 1),
 	IDE_TFLAG_IN_NSECT		= (1 << 25),
 	IDE_TFLAG_IN_LBAL		= (1 << 26),
 	IDE_TFLAG_IN_LBAM		= (1 << 27),
@@ -956,6 +957,8 @@
 extern void SELECT_DRIVE(ide_drive_t *);
 void SELECT_MASK(ide_drive_t *, int);
 
+u8 ide_read_error(ide_drive_t *);
+
 extern int drive_is_ready(ide_drive_t *);
 
 void ide_pktcmd_tf_load(ide_drive_t *, u32, u16, u8);
@@ -1357,11 +1360,4 @@
 
 	return &hwif->drives[(drive->dn ^ 1) & 1];
 }
-
-static inline u8 ide_read_error(ide_drive_t *drive)
-{
-	ide_hwif_t *hwif = drive->hwif;
-
-	return hwif->INB(hwif->io_ports.error_addr);
-}
 #endif /* _IDE_H */