arm64: enable its-migration tests for TCG

With the support for TCG emulated GIC we can also test these now.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Cc: Shashi Mallela <shashi.mallela@linaro.org>
Message-Id: <20210525172628.2088-4-alex.bennee@linaro.org>
Signed-off-by: Andrew Jones <drjones@redhat.com>