riscv: kexec: Avoid deadlock in kexec crash path

In the Linux kernel, the following vulnerability has been resolved:

riscv: kexec: Avoid deadlock in kexec crash path

If the kexec crash code is called in the interrupt context, the

machine_kexec_mask_interrupts() function will trigger a deadlock while

trying to acquire the irqdesc spinlock and then deactivate irqchip in

irq_set_irqchip_state() function.

Unlike arm64, riscv only requires irq_eoi handler to complete EOI and

keeping irq_set_irqchip_state() will only leave this possible deadlock

without any use. So we simply remove it.