x86: re-arrange order of decode for various EVEX opcodes

x86: re-arrange order of decode for various EVEX opcodes

The order of decodes influences the overall number of table entries.
Reduce table size quite a bit by first decoding few-alternatives
attributes common to all valid leaves.

This also adds a PREFIX_DATA 7531c61332db ("x86: simplify decode of
opcodes valid with (embedded) 66 prefix only") missed to apply to
vbroadcastf64x4.