x86/kvm: Always inline evmcs_write64()

vmlinux.o: warning: objtool: vmx_update_host_rsp()+0x64: call to evmcs_write64() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210624095148.126956644@infradead.org