xen/arm: Make gic-v2 code handle hip04-d01 platform

xen/arm: Make gic-v2 code handle hip04-d01 platform

The GIC in this platform is mainly compatible with the standard
GICv2 beside:
- ITARGET is extended to 16 bit to support 16 CPUs;
- SGI mask is extended to support 16 CPUs;
- maximum supported interrupt is 510;
- GICH APR and LR register offsets.

Signed-off-by: Frediano Ziglio <frediano.ziglio@huawei.com>
Signed-off-by: Zoltan Kiss <zoltan.kiss@huawei.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>