sparc/ftrace: Fix ftrace graph time measurement

sparc/ftrace: Fix ftrace graph time measurement

The ftrace function_graph time measurements of a given function is not
accurate according to those recorded by ftrace using the function
filters.  This change pulls the x86_64 fix from 'commit 722b3c746953
("ftrace/graph: Trace function entry before updating index")' into the
sparc specific prepare_ftrace_return which stops ftrace from
counting interrupted tasks in the time measurement.

Example measurements for select_task_rq_fair running "hackbench 100
process 1000":

              |  tracing/trace_stat/function0  |  function_graph
 Before patch |  2.802 us                      |  4.255 us
 After patch  |  2.749 us                      |  3.094 us

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(Cherry picked from commit 48078d2dac0a26f84f5f3ec704f24f7c832cce14)

Note: Upstream fix needed an extra parameter of NULL for
prepare_ftrace_return.

Orabug: 25995351

Signed-off-by: Allen Pais <allen.pais@oracle.com>
Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>