ACPI / SPI: Use parent's ACPI_HANDLE() in acpi_register_spi_devices()

The ACPI handle of struct spi_master's dev member should not be
set, because this causes that struct spi_master to be associated
with the ACPI device node corresponding to its parent as the
second "physical_device", which is incorrect (this happens during
the registration of struct spi_master).  Consequently,
acpi_register_spi_devices() should use the ACPI handle of the
parent of the struct spi_master it is called for rather than that
struct spi_master's ACPI handle (which should be NULL).

Make that happen and modify the spi-pxa2xx driver, which currently is
the only driver for ACPI-enumerated SPI controller chips, not to set
the ACPI handle for the struct spi_master it creates.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>