[NVPTX][DEBUGINFO]Temp workaround for crash of ptxas: disable packed bytes in debug sections.

Summary:
This patch works around the bug in the ptxas tool with the processing of bytes
separated by the comma symbol. The emission of the packed string is
temporarily disabled.

Reviewers: tra

Subscribers: jholewinski, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59148

llvm-svn: 355740