[S390] tape: remove f_pos changes from read / write function.

The change to f_pos in the read / write method has no effect as the
value is controlled by the VFS layer, e.g. for vfs_read:

	loff_t pos = file_pos_read(file);
	ret = vfs_read(file, buf, count, &pos);
	file_pos_write(file, pos);
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/tape_char.c

@@ -170,7 +170,6 @@ tapechar_read(struct file *filp, char __user *data, size_t count, loff_t *ppos)
 	if (rc == 0) {
 		rc = block_size - request->rescnt;
 		DBF_EVENT(6, "TCHAR:rbytes:  %x\n", rc);
-		filp->f_pos += rc;
 		/* Copy data from idal buffer to user space. */
 		if (idal_buffer_to_user(device->char_data.idal_buf,
 					data, rc) != 0)
@@ -238,7 +237,6 @@ tapechar_write(struct file *filp, const char __user *data, size_t count, loff_t
 			break;
 		DBF_EVENT(6, "TCHAR:wbytes: %lx\n",
 			  block_size - request->rescnt);
-		filp->f_pos += block_size - request->rescnt;
 		written += block_size - request->rescnt;
 		if (request->rescnt != 0)
 			break;