scripts/faddr2line: make the new code listing format optional

Commit 6870c016 ("scripts/faddr2line: show the code context")
radically altered the output format of the faddr2line tool.  And while
the new list output format might have merit it broke my vim usage and
was hard to read.

Make the new format optional; using a '--list' argument and attempt to
make the output slightly easier to read by adding a little whitespace to
separate the different files and explicitly mark the line in question.

Cc: Changbin Du <changbin.du@intel.com>
Fixes: 6870c016

 ("scripts/faddr2line: show the code context")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>