PCI: xilinx-xdma: Fix uninitialized symbols in xilinx_pl_dma_pcie_setup_irq()

The error paths that follow calls to the devm_request_irq() functions
within the xilinx_pl_dma_pcie_setup_irq() reference an uninitialized
symbol each that also so happens to be incorrect.

Thus, fix this omission and reference the correct variable when invoking
a given dev_err() function following an error.

This problem was found using smatch via the 0-DAY CI Kernel Test service:

  drivers/pci/controller/pcie-xilinx-dma-pl.c:638 xilinx_pl_dma_pcie_setup_irq() error: uninitialized symbol 'irq'.
  drivers/pci/controller/pcie-xilinx-dma-pl.c:645 xilinx_pl_dma_pcie_setup_irq() error: uninitialized symbol 'irq'.

Fixes: 8d786149

 ("PCI: xilinx-xdma: Add Xilinx XDMA Root Port driver")
Link: https://lore.kernel.org/oe-kbuild/202312120248.5DblxkBp-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202312120248.5DblxkBp-lkp@intel.com/
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>