Unlike system call numbers the assignment of si_codes has never had a
reason to be made per architecture.  Some architectures have had unique
conditions to report and reporting those conditions needed new si_codes.
Nothing has ever needed si_codes to have different values on different
architectures.  The si_code space is vast so even with defining all
si_codes on all architectures there is no danger in running out of
si_code values.

The history of the si_codes BUS_MCEERR_AR, BUS_MCEER_AO, SEGV_BNDERR,
and SEGV_PKUERR show that a need of one architecture frequently becomes
a need of another architecture which makes sharing si_codes between
architectures a positive benefit and something to be encouraged.

Where there are no conflicts with the historical ia64 arch specific
si_codes and any other si_codes make them generic si_codes.  We might
need them on another architecture someday.

This leaves only the good example of arch generic si_codes in the kernel
for future architectures and architecture enhancments to follow.
Without bad examples to follow it should be easy to avoid the mistakes
of the past.
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
[arnd: took Eric's changelog text]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>