USB: bcma: use module_bcma_driver to simplify the code

module_bcma_driver() makes the code simpler by eliminating
boilerplate code.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Link: https://lore.kernel.org/r/20200918030830.3946254-1-liushixin2@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>