Inconsistent R_SPARC_RELATIVE addend handling

[David Miller]

From: James Clarke <jrtc27@jrtc27.com>
Date: Fri, 8 Dec 2017 11:29:37 +0000

> Therefore I am posing two questions:
> 
> 1. Can we change sparc32 to assign rather than add, or does it need to stay
>    like this for compatibility?
> 
> 2. Can we make sparc64 consistent with itself, and if so, should it be
>    assigning or adding?

I think we should leave the addition in there for sparc32 to avoid
potentially breaking any existing binaries.

As per sparc64, if it has gotten away with doing an assignment for
RELA all of this time we should keep it that way and make sparc64
consistent with itself.