KVM: x86: Make kvm_pio_request.linear_rip a common field for user exits

Move and rename kvm_pio_request.linear_rip to
kvm_vcpu_arch.cui_linear_rip so that the field can be used by other
userspace exit completion flows that need to take action if and only
if userspace has not modified RIP.

No functional changes intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Manali Shukla <manali.shukla@amd.com>
Link: https://lore.kernel.org/r/20250502050346.14274-2-manali.shukla@amd.com


Signed-off-by: Sean Christopherson <seanjc@google.com>