hw-breakpoint interfaces for BookE - ver I

Hi All,
Please find a patch that implements hardware-breakpoint interfaces for
BookE processors. The patches are under continuous development and are sent to receive early comments. For the moment, they are (only) compile tested (with ppc64e_defconfig), further testing will accompany the ongoing development.

A few notes about the patchset, as below:
- The patch is designed with reference to BookIII-E type processors specification (having two DAC/DVC registers).
- Instruction breakpoint requests are not implemented through the generic breakpoint interfaces. Such requests are still possible for user-space through ptrace.
- Breakpoint exceptions are designed to 'trigger-after-execute', although the processors raise the exception before instruction execution. To achieve this, the causative insruction is single-stepped over and the breakpoint handler is invoked in the ICMP exception handler.
- The patches are dependant on the recent submissions (not yet integrated into mainline) that bring support for hw-breakpoint weight (patchset from Frederic Weisbecker LKML ref:[email protected]) and PPC64 hw-breakpoint support (linuxppc-dev ref:[email protected]).

Here are a few items identified to work upon in the successive versions. TO DO
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- Modify ptrace requests to use the generic hw-breakpoint interfaces (PTRACE_<GET><SET>_DEBUGREG, PTRACE_SETHWDEBUG)
- Explore intergration of BookE and BookS code intergration (hw_breakpoint.c and hw_breakpoint_booke.c)
- Code clean-up and reduction.

Kindly let me know about comments/suggestions, if any.

Thank You,
K.Prasad