package/libvirt: drop reference to legacy BR2_PACKAGE_QEMU_CUSTOM_TARGETS

Commit 44be514b21fd9409 (package/qemu: refactor target emulator selection)
dropped BR2_PACKAGE_QEMU_CUSTOM_TARGETS, but didn't remove the reference
from libvirt.  Fix that.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libvirt/Config.in

@@ -73,7 +73,7 @@ config BR2_PACKAGE_LIBVIRT_QEMU
 	select BR2_PACKAGE_HWDATA_PCI_IDS # libpciaccess
 	select BR2_PACKAGE_LIBSECCOMP
 	select BR2_PACKAGE_QEMU
-	select BR2_PACKAGE_QEMU_SYSTEM if BR2_PACKAGE_QEMU_CUSTOM_TARGETS = ""
+	select BR2_PACKAGE_QEMU_SYSTEM
 	select BR2_PACKAGE_YAJL
 	help
 	  QEMU/KVM support