irqchip/sg2042-msi: Set MSI_FLAG_MULTI_PCI_MSI flags for SG2044

The MSI controller on SG2044 has the ability to allocate multiple PCI MSI
interrupts. So the PCIe controller driver can use this feature if the
hardware supports multiple PCI MSI interrupts.

Add the MSI_FLAG_MULTI_PCI_MSI flag to the supported_flags of SG2044
msi_parent_ops to enable this functionality.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Chen Wang <unicorn_wang@outlook.com> # Pioneerbox
Reviewed-by: Chen Wang <unicorn_wang@outlook.com>
Link: https://lore.kernel.org/all/20250813232835.43458-5-inochiama@gmail.com