PCI: uniphier: Use INTX instead of legacy

In the Designware uniphier controller driver, including the endpoint
driver, change all names using "legacy" to use "intx", to match the
term used in the PCI specifications.

Link: https://lore.kernel.org/r/20231122060406.14695-14-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>