bitmap: Remove dead code, i.e. bitmap_copy_le()

Besides the fact it's not used anywhere it should be implemented
differently, i.e. via helpers from linux/byteorder/generic.h.
Yet the helpers themselves need to be introduced first.

Also note, the function lacks of the test cases, they must be provided.

Hence, drop the current dead code for good.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>