The code was using the number of source operands plus one. The plus one
seems to be an ARM specific value accounting for one of the source
operands having 2 sub operands. No other target in tree uses
PseudoLowering with variadic instructions so this worked.
This patch replaces it with a proper count of the number of sub operands
of all operands. While there I update the loop to use MIOperandNo so we
don't need to count up the sub operands as we go.
009971a0d3