kvmtool: arm64: fix compilation error

Currently tools/kvm doesn't build on arm64 when gtk3 is present.  The error looks like this:

  LINK     lkvm
ui/gtk3.o: In function `kvm_gtk_key_press':
/extra/sb/linux-kvm/tools/kvm/ui/gtk3.c:201: undefined reference to `kbd_queue'
/extra/sb/linux-kvm/tools/kvm/ui/gtk3.c:204: undefined reference to `kbd_queue'
/extra/sb/linux-kvm/tools/kvm/ui/gtk3.c:216: undefined reference to `kbd_queue'
/extra/sb/linux-kvm/tools/kvm/ui/gtk3.c:217: undefined reference to `kbd_queue'
/extra/sb/linux-kvm/tools/kvm/ui/gtk3.c:218: undefined reference to `kbd_queue'
ui/gtk3.o:/extra/sb/linux-kvm/tools/kvm/ui/gtk3.c:219: more undefined references to `kbd_queue' follow
collect2: error: ld returned 1 exit status
make: *** [lkvm] Error 1

The patch below makes the error go away and the resulting lkvm runs on arm64.

Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Joel Schopp <joel.schopp@amd.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>