Well we're talking about Intel and AMD and I thought we should also remember there are more chip makers out there that would have an interest in decoding encrypted content.
But I seriously doubt that ARM chipmakers not getting access to DRM core would constitute anti-competitive behaviour.
Especially since these are completely different markets who do most stuff differently. Thats what I wanted to point out - if they want their chips to play DRM content they'll have to negotiate it themselves with the Hollywood. I also strongly suspect that this is not an exclusive pact.
Since nowadays content producers are very well aware that more and more (probably the majority?) of content is consumed via - non x86 architecture devices.