KVM: SVM: Don't BUG if userspace injects an interrupt with GIF=0

In the Linux kernel, the following vulnerability has been resolved:

KVM: SVM: Don't BUG if userspace injects an interrupt with GIF=0

Don't BUG/WARN on interrupt injection due to GIF being cleared,
since it's trivial for userspace to force the situation via
KVM_SET_VCPU_EVENTS (even if having at least a WARN there would be correct
for KVM internally generated injections).

kernel BUG at arch/x86/kvm/svm/svm.c:3386!
invalid opcode: 0000 [#1] SMP
CPU: 15 PID: 926 Comm: smm_test Not tainted 5.17.0-rc3+ #264
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:svm_inject_irq+0xab/0xb0 [kvm_amd]
Code: <0f> 0b 0f 1f 00 0f 1f 44 00 00 80 3d ac b3 01 00 00 55 48 89 f5 53
RSP: 0018:ffffc90000b37d88 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88810a234ac0 RCX: 0000000000000006
RDX: 0000000000000000 RSI: ffffc90000b37df7 RDI: ffff88810a234ac0
RBP: ffffc90000b37df7 R08: ffff88810a1fa410 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff888109571000 R14: ffff88810a234ac0 R15: 0000000000000000
FS: 0000000001821380(0000) GS:ffff88846fdc0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f74fc550008 CR3: 000000010a6fe000 CR4: 0000000000350ea0
Call Trace:
<TASK>
inject_pending_event+0x2f7/0x4c0 [kvm]
kvm_arch_vcpu_ioctl_run+0x791/0x17a0 [kvm]
kvm_vcpu_ioctl+0x26d/0x650 [kvm]
__x64_sys_ioctl+0x82/0xb0
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae
</TASK>