drm/amdkfd: add send exception operation

Add a debug operation that allows the debugger to send an exception
directly to runtime through a payload address.

For memory violations, normal vmfault signals will be applied to
notify runtime instead after passing in the saved exception data
when a memory violation was raised to the debugger.

For runtime exceptions, this will unblock the runtime enable
function which will be explained and implemented in a follow up
patch.

Signed-off-by: Jonathan Kim <jonathan.kim@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>