package/udev: add the missing sgx group

systemd-udevd needs this group:
  /usr/lib/udev/rules.d/50-udev-default.rules:43 Unknown group 'sgx', ignoring

Signed-off-by: TIAN Yuanhao <tianyuanhao3@163.com>
[yann.morin.1998@free.fr: udev users/groups go to udev virtual package]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/udev/udev.mk

@@ -9,6 +9,7 @@ define UDEV_USERS
 	- - input -1 * - - - Input device group
 	- - render -1 * - - - DRI rendering nodes
 	- - kvm -1 * - - - kvm nodes
+	- - sgx -1 * - - - SGX device nodes
 endef
 
 $(eval $(virtual-package))