arm64: fix calling nmi_enter() repeatedly when IPI_CPU_CRASH_STOP

hulk inclusion
category: bugfix
bugzilla: 28145
CVE: NA

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The nmi_enter() may has been called in el1_irq. When processing
IPI_CPU_CRASH_STOP in handle_IPI(), don't call nmi_enter() again if
interrupt is disabled (already in NMI context).

Fixes: e753aae7e448 ("arm64: Fix interrupt tracing in the presence of NMIs")
Signed-off-by: Wei Li <liwei391@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>