spi: dw-pci: fix bug when regs left uninitialized

The commit 04f421e7 "spi: dw: use managed resources" changes drivers to use
managed functions, but seems wasn't properly tested in PCI case. The regs field
of struct dw_spi left uninitialized. Thus, kernel crashes when tries to access
to the SPI controller registers. This patch fixes the issue.

Fixes: 04f421e7

 (spi: dw: use managed resources)
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org