Kernel 3.2 bladeRF fix by cbalke

The problem with bladerf on kernel 3.2 and below is that the module_usb_driver macro is missing on older kernels.
The fix below basically bypasses the macro
If someone can put this onto github it would be helpful.
I tested this patch on kernel 3.2.6


To fix this problem with kernel 3.2 and below...

Replace this line :

module_usb_driver(bladerf_driver);

------------------with the lines below-------------

static int __init bladerf_init(void)
{
        return usb_register(&bladerf_driver);
}
static void __exit bladerf_exit(void)
{
        usb_deregister(&bladerf_driver);
}
module_init(bladerf_init);
module_exit(bladerf_exit);