xtensa: move spill_registers to traps.h

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
xtensa: add support for oprofile

Support call graph profiling.
Keep upper two bits of PC unchanged through backtrace rather than take
them from sp (a1). The stack pointer is usually in the same GB (same
upper 2 bits) as PC, but technically doesn't always have to be (and
might not in the future, when taking full advantage of MMU v3).

Signed-off-by: Dan Nicolaescu <dann@xtensa-linux.org>
Signed-off-by: Pete Delaney <piet@tensilica.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
xtensa: complete ptrace handling of register windows

Compute WindowBase and WindowMask registers correctly on ptrace calls.
Work done earlier by Maxim, Christian and Marc.

Signed-off-by: Marc Gauthier <marc@tensilica.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>