firmware: Update hotplug script

Update the in-kernel hotplug example script to work
properly with recent kernels. Without this fix the
script may load the firmware twice - both at "add"
and "remove" time.

The second load only triggers in the case when multiple
firmware images are used. A good example is the b43
driver which does not work properly without this fix.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>