KVM: x86: rename process_smi to enter_smm, process_smi_request to process_smi

Make the function names more similar between KVM_REQ_NMI and KVM_REQ_SMI.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>