perf annotate: Use arch->objdump.comment_char in dec__parse()

perf annotate: Use arch->objdump.comment_char in dec__parse()

Presume neglected in commit 786c1b5 "perf annotate: Start supporting
cross arch annotation".  This doesn't fix a bug since none of the
affected arches support parsing dec/inc instructions yet.

Signed-off-by: Kim Phillips <kim.phillips@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Chris Ryder <chris.ryder@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20161130092333.1cca5dd2c77e1790d61c1e9c@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>