arm64: remove invalid check from its-trigger test

While an IRQ is not "guaranteed to be visible until an appropriate
invalidation" it doesn't stop the actual implementation delivering it
earlier if it wants to. This is the case for QEMU's TCG and as tests
should only be checking architectural compliance this check is
invalid.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Cc: Shashi Mallela <shashi.mallela@linaro.org>
Message-Id: <20210525172628.2088-2-alex.bennee@linaro.org>
Signed-off-by: Andrew Jones <drjones@redhat.com>