misc: pci_endpoint_test: Skip IRQ tests if irq is out of range

The pci_endpoint_test tests the 32-bit MSI range. However, the device might
not have all vectors configured. For example, if msi_interrupts is 8 in the
ep function space or if the MSI Multiple Message Capable value is
configured as 4 (maximum 16 vectors).

In this case, do not attempt to run the test to avoid timeouts and directly
return the error value.

Signed-off-by: Christian Bruel <christian.bruel@foss.st.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20250804170916.3212221-2-christian.bruel@foss.st.com