This is a cleanup of the series of tests I added some time ago.

During the latest reviews, I got comments about the fact that some
intrinsics do not support all the vector types but the corresponding
tests would still contain dummy expected results for those variants.

This patch cleans this up, by:
* removing all these dummy expected values
* where needed, checking results of each variant rather than relying
on the general macro which tests all the variants, to save coding
lines.

Maybe it's a bit big, but it's mostly mechanical.

Tested on ARM and AArch64 (LE/BE) using qemu.

OK for trunk?

Thanks,

Christophe