KVM: VMX: Rename NMI_PENDING to NMI_WINDOW

[ Upstream commit 4e2a0bc56ad197e5ccfab8395649b681067fe8cb ]

Rename the NMI-window exiting related definitions to match the latest
Intel SDM. No functional changes.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Stable-dep-of: 31de69f4eea7 ("KVM: nVMX: Properly expose ENABLE_USR_WAIT_PAUSE control to L1")
Signed-off-by: Sasha Levin <sashal@kernel.org>