plat/qemu: move gicv2 codes to separate file

This file moves gicv2 codes to a new separate files, target is to add
gicv3 support later.

Signed-off-by: Hongbo Zhang <hongbo.zhang@linaro.org>
Reviewed-by: Radoslaw Biernacki <radoslaw.biernacki@linaro.org>
Tested-by: Radoslaw Biernacki <radoslaw.biernacki@linaro.org>
Change-Id: I30eb1fda5ea5c2b35d79360c52f46601cbca1bcc
6 files changed