qd65xx: use IDE_HFLAG_SINGLE host flag

* Set IDE_HFLAG_SINGLE host flag in qd_probe() for QD6500 and QD6580
  with the second port disabled.

* Check for IDE_HFLAG_SINGLE in qd6580_port_init_devs() instead of
  using cached value of QD6580 Control register.

* Don't cache QD6580 Control register value in hwif->config_data
  (bits 8-15) and remove no longer needed QD_CONTROL() macro.

* Cache QD65xx base address in hwif->config_data (bits 8-15)
  instead of hwif->select_data.

* Set hwif->config_data in qd_probe() and remove qd_setup() helper.

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