braodcom/vc5: Rely on OVRTMUOUT always being set.

braodcom/vc5: Rely on OVRTMUOUT always being set.

It seems that the HW team has decided that it's the only supported mode,
and it's the mode I actually meant to be using but forgot.  Our table of
return_32_bit should have matched the default non-OVRTMUOUT behavior, so
this change should be invisible.

However, the change revealed that some my return_size checks for swizzling
were a bit confused in the shadow case, so I had to move them to draw time
once we have both the sampler and the view together.

Fixes assertion failures in the updated simulator, where the non-OVRTMUOUT
support has been removed.