PCI: endpoint: Add intx_capable to epc_features struct

In struct pci_epc_features, an EPC driver can already specify if they
support MSI (by setting msi_capable) and MSI-X (by setting msix_capable).

Thus, for consistency, allow an EPC driver to specify if it supports
INTx interrupts as well (by setting intx_capable).

Since this struct is zero initialized, EPC drivers that want to claim
INTx support will need to set intx_capable to true.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
[kwilczynski: add missing kernel-doc for "intx_capable"]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Link: https://lore.kernel.org/r/20250310111016.859445-13-cassel@kernel.org

Author: floatious

include/linux/pci-epc.h

@@ -221,13 +221,15 @@ struct pci_epc_bar_desc {
  * @linkup_notifier: indicate if the EPC device can notify EPF driver on link up
  * @msi_capable: indicate if the endpoint function has MSI capability
  * @msix_capable: indicate if the endpoint function has MSI-X capability
+ * @intx_capable: indicate if the endpoint can raise INTx interrupts
  * @bar: array specifying the hardware description for each BAR
  * @align: alignment size required for BAR buffer allocation
  */
 struct pci_epc_features {
 	unsigned int	linkup_notifier : 1;
 	unsigned int	msi_capable : 1;
 	unsigned int	msix_capable : 1;
+	unsigned int	intx_capable : 1;
 	struct	pci_epc_bar_desc bar[PCI_STD_NUM_BARS];
 	size_t	align;
 };