PCI: endpoint: Rename LEGACY to INTX in test function driver

In the endpoint test function driver, rename IRQ_TYPE_LEGACY to
IRQ_TYPE_INTX and COMMAND_RAISE_LEGACY_IRQ to COMMAND_RAISE_INTX_IRQ
to match the term used in the PCI specifications.

Link: https://lore.kernel.org/r/20231122060406.14695-5-dlemoal@kernel.org


Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>