PCI: cadence: Use INTX instead of legacy

In the Cadence endpoint controller driver, rename the function
cdns_pcie_ep_send_legacy_irq() to cdns_pcie_ep_send_intx_irq() to match
the macro PCI_IRQ_INTX name. Related comments and messages mentioning
"legacy" are also changed to refer to "intx".

Link: https://lore.kernel.org/r/20231122060406.14695-9-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>