Add missing VLD alignment options to the assembler
- "VLD single element to all lanes" had the alignment options listed incorrectly, preventing them from working. Fix by adding a dummy option for 8 bit alignment, like "VLD single element to all lanes".
- "VLD single 4-element structure to all lanes" was missing support for 32 bit elements with 64 bit alignment.
- Add extra instructions to TestVFP to test all the different "single to all lanes" alignment options.