scripts/faddr2line: fix location of start_kernel in comment

Fix a source file reference location to the correct path name.

Link: http://lkml.kernel.org/r/1d50bd3d-178e-dcd8-779f-9711887440eb@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>