demmt: fix formatting of the first line of macro disassembly
demmt: drop "restart pushbuf" messages when those restarts do not matter

This code (and the one in a while loop later, for PUSH type) should
be dropped when we'll be sure other methods of pushbuf detection work
for all card families. I don't have enough traces to confirm that.
demmt: automatically detect pushbufs (-f/-n not needed)
demmt: fix description of -a option