mprotect/mprotect04.c: add PROT_NONE, PROT_EXEC flag test

create a new case to test PROT_NONE, PROT_EXEC flag for mprotect(2)

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>
Reviewed-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>