wimax/i2400m: Allow bus-specific driver to specify retry count

The code that sets up the i2400m (firmware load and general driver
setup after it) includes a couple of retry loops.

The SDIO device sometimes can get in more complicated corners than the
USB one (due to its interaction with other SDIO functions), that
require trying a few more times.

To solve that, without having a failing USB device taking longer to be
considered dead, allow the retry counts to be specified by the
bus-specific driver, which the general driver takes as a parameter.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>