irqchip/irq-mvebu-sei: Switch to MSI parent

All platform MSI users and the PCI/MSI code handle per device MSI domains
when the irqdomain associated to the device provides MSI parent
functionality.

Remove the "global" platform domain related code and provide the MSI parent
functionality by filling in msi_parent_ops.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Shivamurthy Shastri <shivamurthy.shastri@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240623142235.820275215@linutronix.de