ptxed, block: do not modify the block while printing

When we print a block, we update block.ninsn and block.ip in order to get the IP
for reporting decode errors right.  This has been addressed in the previous
patch so we can now stop updating block.

Change-Id: Ieffa51dfc5006c015dafe6278e3718d495ccccb6
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>