sparc: add '32' suffix to reg_window, sigcontext, __siginfo_t

Renaming a few types to contain a 32 suffix makes the
type names compatible with sparc64 and thus makes sharing
between the two a lot easier.

Note: None of these definitions are expected part of the
stable ABI towards userspace.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>