LoongArch: KVM: Add address alignment check in pch_pic register access

With pch_pic device, its register is based on MMIO address space,
different access size 1/2/4/8 is supported. And base address should
be naturally aligned with its access size, here add alignment check
in its register access emulation function.

Cc: stable@vger.kernel.org
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>