spi: dw-pci: fix typo

spi: dw-pci: fix typo

Commit 04f421e7b0b10 (spi: dw: use managed resources) introduced a typo in
struct field reference. Fix it.

Fixes build failure:

drivers/spi/spi-dw-pci.c: In function 'spi_pci_probe':
drivers/spi/spi-dw-pci.c:50:29: error: 'dev' undeclared (first use in this function)
  dwpci = devm_kzalloc(&pdev-dev, sizeof(struct dw_spi_pci), GFP_KERNEL);
                             ^

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Mark Brown <broonie@linaro.org>