spi/pxa2xx-pci: correct the return value check of pcim_iomap_regions()

The function returns 0 on success and negative errno in case of failure.
Fix this.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>