Fix: save/rstr irqs in tracing inst. of dis/enable
Optimize nvklimirqd thread lookup.

This patch optimizes the routines used to look up
the nvklmirqd thread instance mapped for each GPU.
Most significant optimization is the replacement
of a spinlock with a reader/writer mutex (writes
only take place during scheduler initialization time).
Clean up plugin activation.

This patch cleans up plugin activation to match
mainline litmus. Patch was manual. Merge conflicts
will have to be resolved in the future.
Refactor overhead and sched-trace external APIs

Splits the external APIs for sched-trace and overhead
tracing into two files. This allows the kernel to be
compiled for only overhead or only sched-trace tracing
and still have functioning external trace APIs

(External trace APIs are used by patched versions of
 the GPL-layer of NVIDIA's drivers)
Simplify klmirqd initialization

This patch simplifies klmirqd's initialization. Initialization
now performed via static assignment. init_klmirqd() stub remains
for the future.
Minor debug tracing enhancements to sched_cedf.c