x86, um: get rid of uml unistd.h

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/um/kernel/exec.c b/arch/um/kernel/exec.c
index 598711c..fda30d2 100644
--- a/arch/um/kernel/exec.c
+++ b/arch/um/kernel/exec.c
@@ -15,6 +15,7 @@
 #include "mem_user.h"
 #include "skas.h"
 #include "os.h"
+#include "internal.h"
 
 void flush_thread(void)
 {