ptxed, block: extract fetching an instruction
ptxed, block: extract fetching an instruction

Extract the code for fetching an instruction from a block into a separate
function.  We will need it in a few more places.

Change-Id: Ibe676184f37f8328a4b684ff7d13a6d38fe8aa82
Signed-off-by: Markus Metzger <5f675b2b36595f90898e014b548ff7d9bbff2ab7@intel.com>

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