DEBUG_SPINLOCK_BUG_ON can be used with both vgic-v2 and vgic-v3,
so let's move it to vgic.h
Signed-off-by: NJia He <jia.he@hxt-semitech.com>
[maz: commit message tidy-up]
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>