docs: kvm: api.rst: add missing spaces

There are some warnings:

   Documentation/virt/kvm/api.rst:4354: WARNING: Definition list ends without a blank line; unexpected unindent.
   Documentation/virt/kvm/api.rst:4358: WARNING: Definition list ends without a blank line; unexpected unindent.
   Documentation/virt/kvm/api.rst:4363: WARNING: Definition list ends without a blank line; unexpected unindent.

Produced by the lack of identation on a single line. That
caused the literal block to end prematurely.
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/b6b3679b6c2329dc9b16d397c289b5ade0184c63.1599660067.git.mchehab+huawei@kernel.orgSigned-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/virt/kvm/api.rst

@@ -4343,7 +4343,7 @@ Errors:
   #define KVM_STATE_NESTED_VMX_SMM_GUEST_MODE	0x00000001
   #define KVM_STATE_NESTED_VMX_SMM_VMXON	0x00000002
 
-#define KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE 0x00000001
+  #define KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE 0x00000001
 
   struct kvm_vmx_nested_state_hdr {
 	__u64 vmxon_pa;