misc: pci_endpoint_test: Fix 'irq_type' to convey the correct type

There are two variables that indicate the interrupt type to be used
in the next test execution, "irq_type" as global and "test->irq_type".

The global is referenced from pci_endpoint_test_get_irq() to preserve
the current type for ioctl(PCITEST_GET_IRQTYPE).

The type set in this function isn't reflected in the global "irq_type",
so ioctl(PCITEST_GET_IRQTYPE) returns the previous type.

As a result, the wrong type is displayed in old version of "pcitest"
as follows:

  - Result of running "pcitest -i 0"

      SET IRQ TYPE TO LEGACY:         OKAY

  - Result of running "pcitest -I"

      GET IRQ TYPE:           MSI

Whereas running the new version of "pcitest" in kselftest results in an
error as follows:

  #  RUN           pci_ep_basic.LEGACY_IRQ_TEST ...
  # pci_endpoint_test.c:104:LEGACY_IRQ_TEST:Expected 0 (0) == ret (1)
  # pci_endpoint_test.c:104:LEGACY_IRQ_TEST:Can't get Legacy IRQ type

Fix this issue by propagating the current type to the global "irq_type".

Fixes: b2ba9225 ("misc: pci_endpoint_test: Avoid using module parameter to determine irqtype")
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250225110252.28866-5-hayashi.kunihiko@socionext.com