irqchip/riscv-imsic: Avoid interrupt translation in interrupt handler

Currently, imsic_handle_irq() uses generic_handle_domain_irq() to handle
the interrupt, which internally has an extra step of resolving hwirq using
domain.

Avoid the translation step by replacing the hardware interrupt number with
the Linux interrupt number in the IMSIC vector data and directly call
generic_handle_irq().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250217085657.789309-10-apatel@ventanamicro.com