ide-tape: fix build issue

This fixes

drivers/ide/ide-tape.c: In function `idetape_chrdev_open':
drivers/ide/ide-tape.c:1515: error: implicit declaration of function `idetape_read_position'
make[1]: *** [drivers/ide/ide-tape.o] Error 1

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>