[RFC PATCH v3 0/3] ARM: VFP: Save / restore VFP state on the signal handler path

[imre.deak at nokia.com]

This fixes a VFP corruption problem in a process's main thread, when
both the main thread and a signal handler triggered for the process
uses floating point ops.

Changes since v2 according to Russell's comments and patches:
- refactor vfp_sync_state to make it clearer
- break vfp_sync_state into vfp_{save/restore}_hwstate for efficiency
- Keep the additional VFP exception registers in a separate struct. This
  way we'll keep the existing ABI intact.

--Imre