PCI: rockchip-host: Rename rockchip_pcie_legacy_int_handler()

Rename the function rockchip_pcie_legacy_int_handler() of the rockchip
host driver to rockchip_pcie_intx_handler() to match the PCI_IRQ_INTX
macro name used to control this function execution, and to match the
term used in the PCI specifications.

Link: https://lore.kernel.org/r/20231122060406.14695-16-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>