loongarch/kvm: ls7a add iocsrw emulation

LoongArch inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6MUZX



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The virtual machine has a case where the LS7A registers
 are accessed in length 4 bytes, so the emulation of
4-byte access to LS7A is added.

Signed-off-by: lixianglai <lixianglai@loongson.cn>
Change-Id: I46daf63d7a1766080a806adbd3f2d6b77f9657d0