target-arm: Add GIC phandle to VirtBoardInfo

Instead of passing the GIC phandle around between functions, add it to
the VirtBoardInfo just like we do for the clock_phandle.  We are about
to add the v2m phandle as well, and it's easier not having to pass
around a bunch of phandles, return multiple values from functions, etc.

Reviewed-by: Eric Auger <eric.auger@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Message-id: 1432897270-7780-2-git-send-email-christoffer.dall@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>