Tidy instruction buffer size usage in preparation for copying the
instruction bytes onto samples.

The instruction buffer is presently used for debugging, so rename its
size macro from INTEL_PT_INSN_DBG_BUF_SZ to INTEL_PT_INSN_BUF_SZ, and
use it everywhere.

Note that the maximum instruction size is 15 which is a less efficient size
to copy than 16, which is why a separate buffer size is used.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1475847747-30994-2-git-send-email-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>