vec_replace_unaligned has wrong type signatures

[openpower-gitea-migrator]

Originally Gitea issue #83 by @wschmidt-ibm on 2022-02-03

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This is a pasto. The type signatures from vec_replace_elt appear here as well. These should be changed so that, for each signature, the return value and first argument are vector unsigned char.

[openpower-gitea-migrator]

@wschmidt-ibm commented on 2022-02-08

Actually, just the return value should be vector unsigned char. The first argument should remain as shown in the document.