irqchip/riscv-imsic: Set irq_set_affinity() for IMSIC base

The IMSIC driver assigns the IMSIC domain specific imsic_irq_set_affinity()
callback to the per device leaf MSI domain. That's a layering violation as
it is called with the leaf domain data and not with the IMSIC domain
data. This prevents moving the IMSIC driver to the common MSI library which
uses the generic msi_domain_set_affinity() callback for device MSI domains.

Instead of using imsic_irq_set_affinity() for leaf MSI domains, use
imsic_irq_set_affinity() for the non-leaf IMSIC base domain and use
irq_chip_set_affinity_parent() for leaf MSI domains.

[ tglx: Massaged change log ]

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250217085657.789309-2-apatel@ventanamicro.com