irqchip/loongson-htvec: Fix potential resource leak

In the function htvec_of_init(), system resource "parent_irq"
was not released in an error case. Thus add a jump target for
the completion of the desired exception handling.

Fixes: 818e915f ("irqchip: Add Loongson HyperTransport Vector support")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1594087972-21715-4-git-send-email-yangtiezhu@loongson.cn