HW-BKPT: Introduce per-cpu breakpoints and modify_kernel_hw_breakpoint API

Hi All,
Please find a set of patches that implement the following:

Patch 1/2: Allow per-cpu kernel-space Hardware Breakpoint requests Patch 2/2: Allow kernel breakpoints to be modified through a new API

During discussion on LKML, these features were deemed necessary for effective exploitation of hardware breakpoints by perf-tools.

The patches are based off -tip tree. Kindly let me know your comments on the same.

Thanks,
K.Prasad