linux-yocto/3.10: fix long perf compile times

linux-yocto/3.10: fix long perf compile times

perf's builtin-sched.c triggers extremly long build times on some
architectures due to gcc 4.7+ var-tracking functionality.

To fix this, we can cherry pick the 3.12 commit:

  f36f83f94 [perf sched: Move struct perf_sched definition out of cmd_sched()]

With this change build times are reduced from 15 to 20 minutes for qemuarm to:

  real    2m19.940s
  user    1m35.438s
  sys     0m11.165s

For kernel's that are not carrying this patch, the following can be added
to the perf recipe to also fix the issue:

    +++ b/meta/recipes-kernel/perf/perf.bb
    @@ -68,6 +68,7 @@ EXTRA_OEMAKE = \
		    CC="${CC}" \
		    AR="${AR}" \
		    perfexecdir=${libexecdir} \
    +               EXTRA_CFLAGS="-fno-var-tracking" \
		    NO_GTK2=1 ${TUI_DEFINES} NO_DWARF=1 ${SCRIPTING_DEFINES} \

(From OE-Core rev: 82ad5305381c2f541ef051a8fc28243cd91776fe)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>