libipt, ild: move opcode map handling in vex decoders
libipt, ild: move opcode map handling in vex decoders

The opcode map is computed from the first payload byte for c4 VEX and EVEX.
Move that computation plus the code that depends on it past the prefix-related
assignments so the life range of the computed map does not overlap with that of
the first payload byte.

Change-Id: I418e53ce769d439cc8801c84ae46abd166853843
Signed-off-by: Markus Metzger <5f675b2b36595f90898e014b548ff7d9bbff2ab7@intel.com>

01org/processor-trace,01org/processor-trace,01org/processor-trace