cmd: fix the order that s390x operands are printed in
The assembler reordered the operands of some instructions to put the
first operand into From3. Unfortunately this meant that when the
instructions were printed the operands were in a different order than
the assembler would expect as input. For example, 'MVC $8, (R1), (R2)'
would be printed as 'MVC (R1), $8, (R2)'.
Originally this was done to ensure that From contained the source
memory operand. The current compiler no longer requires this and so
this CL simply makes all instructions use the standard order for
operands: From, Reg, From3 and finally To.