LoongArch: KVM: Fix base address calculation in kvm_eiointc_regs_access()

In the Linux kernel, the following vulnerability has been resolved: LoongArch: KVM: Fix base address calculation in kvm_eiointc_regs_access() In function kvm_eiointc_regs_access(), the register base address is caculated from array base address plus offset, the offset is absolute value from the base address. The data type of array base address is u64, it should be converted into the "void *" type and then plus the offset.