ide: fix ->io_32bit race in set_io_32bit()

set_io_32bit() (ide_procset_t function) can race against running
PIO transfers.  Fix it by using ide_spin_wait_hwgroup().

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>