um: remove unused mm_copy_segments

It was already removed by commit c17c0204 ("arch: remove unused
*_segments() macros/functions") but seems to have been accidentally
reintroduced by commit 0500871f ("Construct init thread stack in the
linker script rather than by union"). Remove it for good.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/include/asm/processor-generic.h

@@ -59,11 +59,6 @@ static inline void release_thread(struct task_struct *task)
 {
 }
 
-static inline void mm_copy_segments(struct mm_struct *from_mm,
-				    struct mm_struct *new_mm)
-{
-}
-
 /*
  * User space process size: 3GB (default).
  */