ftrace: Remove redundant swap function

ftrace: Remove redundant swap function

To cover the common case of sorting an array of pointers, Daniel
Wagner recently modified the library sort() to use a specific swap
function for size==8, in addition to the size==4 case which was
already handled. Since sizeof(long) is either 4 or 8,
ftrace_swap_ips() is redundant and we can just let sort() pick an
appropriate and fast swap callback.

Link: http://lkml.kernel.org/r/1441834023-13130-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>