spi: dw-pci: free previously allocated IRQs if desc->setup() fails

Free previously allocated IRQs when return an error code of desc->setup()
which is not always successful. And simplify the code by adding a goto
label.

Fixes: 8f5c285f

 ("SPI: designware: pci: Switch over to MSI interrupts")
CC: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Jay Fang <f.fangjian@huawei.com>
Link: https://lore.kernel.org/r/1600132969-53037-1-git-send-email-f.fangjian@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>