irqchip/gic-v3-its: Avoid parsing _indirect_ twice for Device table

In current logic, its_parse_indirect_baser() will be invoked twice
when allocating Device tables. Add a *break* to omit the unnecessary
and annoying (might be ...) invoking.

Fixes: 32bd44dc

 ("irqchip/gic-v3-its: Fix the incorrect parsing of VCPU table size")
Cc: stable@vger.kernel.org
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>