x86: rework AMX control insn disassembly

Consistently do 64-bit first, VEX.L second, VEX.W third, ModR/M fourth,
and only then prefix, resulting in fewer table entries. Note that in the
course of the re-work
- TILEZERO has a previously missing decode step through rm_table[]
  added,
- a wrong M_0 suffix for TILEZERO is also corrected to be M_1 (now an
  infix).