sparc: unify ptrace.h

The two ptrace.h implementations are very alike but
the small differences required two set of ifdef/else/endif pairs.

The definition of reg_window32 could have been shared but
that would have required several updates in sparc32 code as
all printk formatting for example assume it is longs.

sparc_stackf looked like anohter candidate to share if the 32
bit was renamed to sparc_stackf32.
But it contains two pointers in the sparc32 version which would
have been 64 bit in the sparc64 version so it was non-trivial.
Using a set of accessor macros could do the trick if pursued later.

The sparc64 specific definitions are not protected by
ifdef - as it should not be required to do so.

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