staging: otus: remove unused methods

This is rebased version of the patch [1] which was mysteriously not
pushed anywhere but acked.

Here are two methods to convert hex value to binary format. These
certain methods aren't used anywhere in kernel.

[1] http://lkml.org/lkml/2010/2/18/267

Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>