overall_stats: add overall stats for all available cores

this is much more accurate stats tracking than just displaying core 0's
stats from most other kernels

Signed-off-by: faux123 <reioux@gmail.com>

overall_stats: make dual/quad core stats configurable via meunconfig

Signed-off-by: faux123 <reioux@gmail.com>

overall_stats: forward port to kernel 3.4+

by replacing deprecated functions with native add/sub for 64bit data types

Change-Id: I1e17d626bf59b3c0822c9f1088093f848fd2649c
Signed-off-by: faux123 <reioux@gmail.com>