xtensa: implement tracehook functions and enable HAVE_ARCH_TRACEHOOK

Implement syscall_get_nr, syscall_rollback, syscall_get_error,
syscall_{get,set}_return_value and syscall_{get,set}_arguments.
Select HAVE_ARCH_TRACEHOOK as Xtensa now has all support for that.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>