irqchip/riscv-imsic: Move to common MSI library

Simplify the leaf MSI domain handling in the RISC-V IMSIC driver by
using msi_lib_init_dev_msi_info() and msi_lib_irq_domain_select()
provided by the common MSI library.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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/20250217085657.789309-4-apatel@ventanamicro.com