sparc64: Export flush_ptrace_access() (needed by lustre)

ERROR: "flush_ptrace_access" [drivers/staging/lustre/lustre/libcfs/libcfs.ko]
undefined!

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>