arm64: xen: Use existing helper to check interrupt status

mainline inclusion
from mainline-v4.20-rc1
commit b0506a8b
category: bugfix
bugzilla: 9300
CVE: NA

--------------------------------

The status of interrupts might depend on more than just pstate. Use
interrupts_disabled() instead of raw_irqs_disabled_flags() to take the full
context into account.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Wei Li <liwei391@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>