scripts/faddr2line: fix error when addr2line output contains discriminator

scripts/faddr2line: fix error when addr2line output contains discriminator

When addr2line output contains discriminator, the current awk script
cannot parse it.  This patch fixes it by extracting key words using
regex which is more reliable.

  $ scripts/faddr2line vmlinux tlb_flush_mmu_free+0x26
  tlb_flush_mmu_free+0x26/0x50:
  tlb_flush_mmu_free at mm/memory.c:258 (discriminator 3)
  scripts/faddr2line: eval: line 173: unexpected EOF while looking for matching `)'

Link: http://lkml.kernel.org/r/1525323379-25193-1-git-send-email-changbin.du@intel.com
Fixes: 6870c0165feaa5 ("scripts/faddr2line: show the code context")
Signed-off-by: Changbin Du <changbin.du@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: NeilBrown <neilb@suse.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>