sparc,sparc64: unify asm-offsets.c

sparc64 does not use constants generated from asm-offsets
but to prepare it to do so the parts that could be
shared do now generate constants for sparc64 too.

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