PCI: endpoint: pci-epf-test: Expose supported IRQ types in CAPS register

PCI: endpoint: pci-epf-test: Expose supported IRQ types in CAPS register

Expose the supported IRQ types in the CAPS register.

This way, the host side driver (drivers/misc/pci_endpoint_test.c) can
know which IRQ types that the endpoint supports.

The host side driver will make use of this information in a follow-up
commit.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Link: https://lore.kernel.org/r/20250310111016.859445-15-cassel@kernel.org