Force byteable registers for indir op source

Force byteable registers for indir op source

When we have a GT_STOREIND, we need to not only make sure that the
source and dest of the storeind are marked as requiring byteable
registers, but also the indirect op's source. For example:

```
GT_STOREIND(GT_ADD(TYP_INT, mem of TYP_BYTE, reg of TYP_INT or TYP_BYTE))
```

We need to make sure that the source reg of the GT_ADD is byteable.

This change fixes #7224.