firewire: core: fix an information leak

firewire: core: fix an information leak

commit 137d9ebfdbaa45c01f9f0f6d5121ae6f1eb942bd upstream.

If a device exposes a sparsely populated configuration ROM,
firewire-core's sysfs interface and character device file interface
showed random data in the gaps between config ROM blocks.  Fix this by
zero-initialization of the config ROM reader's scratch buffer.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: maximilian attems <max@stro.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>