KVM: SVM: Fix wrong interrupt injection in enable_irq_windows

KVM: SVM: Fix wrong interrupt injection in enable_irq_windows

The nested_svm_intr() function does not execute the vmexit
anymore. Therefore we may still be in the nested state after
that function ran. This patch changes the nested_svm_intr()
function to return wether the irq window could be enabled.

Cc: stable@kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
(Cherry-picked from commit 8fe546547cf6857a9d984bfe2f2194910f3fc5d0)