PCI: tegra194: Set pci_epc_features::msi_capable to true

Since the driver supports MSI, set the flag to true. This helps
pci_endpoint_test to use the optimal IRQ type when using
PCITEST_IRQ_TYPE_AUTO.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
[mani: splitted this change from the bug fix]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20250922140822.519796-6-cassel@kernel.org