wimax/i2400m: retry loading firmware files in sequence

The i2400m firmware loader is given a list of firmware files to try to
load by the probe() function (which can be different based on the
device's model / generation).

Current code didn't attempt to load, check and try to boot with each
file, but just to try to load if off disk. This is limiting in some
cases, where we might want to try to load a firmware and if it fails
to load onto the device, just fall back to another one.

This changes the behaviour so all files are tried for being loaded
from disk, checked and uploaded to the device until one suceeds in
bringing the device up.

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