KVM: vmx: rename pi_init to avoid conflict with paride

allyesconfig results in:

ld: drivers/block/paride/paride.o: in function `pi_init':
(.text+0x1340): multiple definition of `pi_init'; arch/x86/kvm/vmx/posted_intr.o:posted_intr.c:(.init.text+0x0): first defined here
make: *** [Makefile:1164: vmlinux] Error 1

because commit:

commit 8888cdd0996c2d51cd417f9a60a282c034f3fa28
Author: Xiaoyao Li <xiaoyao.li@intel.com>
Date:   Wed Sep 23 11:31:11 2020 -0700

    KVM: VMX: Extract posted interrupt support to separate files

added another pi_init(), though one already existed in the paride code.

Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index e4e7adf..f02962d 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -222,7 +222,7 @@ void pi_wakeup_handler(void)
 	spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, cpu));
 }
 
-void __init pi_init(int cpu)
+void __init pi_init_cpu(int cpu)
 {
 	INIT_LIST_HEAD(&per_cpu(blocked_vcpu_on_cpu, cpu));
 	spin_lock_init(&per_cpu(blocked_vcpu_on_cpu_lock, cpu));