sw64: kvm: expand the number of SWVM_IRQS

Sunway inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5PN9S



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As more devices are hot-plugged in a guest os, it will fail to respond
interrupts because of insufficient interrupt resource and appear to be
stuck.

To fix this issue, expand the maximum number of irq supported to 256.

Signed-off-by: Du Yilong <duyilong@wxiat.com>
Signed-off-by: Gu Zitao <guzitao@wxiat.com>