um: Don't pollute kernel namespace with uapi

Don't include ptrace uapi stuff in arch headers, it will
pollute the kernel namespace and conflict with existing
stuff.
In this case it fixes clashes with common names like R8.

Signed-off-by: Richard Weinberger <richard@nod.at>

arch/x86/um/tls_64.c

@@ -1,4 +1,5 @@
 #include <linux/sched.h>
+#include <asm/ptrace-abi.h>
 
 void clear_flushed_tls(struct task_struct *task)
 {