fix -Wsequence-point error while compilation with 4.9 toolchain 

/home/kau/gum/kernel/lge/msm8226/drivers/cpufreq/cpufreq_interactive.c: In function 'show_target_loads':
/home/kau/gum/kernel/lge/msm8226/drivers/cpufreq/cpufreq_interactive.c:804:6: warning: operation on 'ret' may be undefined [-Wsequence-point]
error, forbidden warning: cpufreq_interactive.c:804
make[4]: *** [drivers/cpufreq/cpufreq_interactive.o] Error 1
make[3]: *** [drivers/cpufreq] Error 2
make[3]: *** Waiting for unfinished jobs....
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this error is fixed by this commit.