[PATCH] libertas: fix RESET logic at unload time

Previously, we had a fixed array of 5 elements where we remembered all
initialized devices. This has been changed to use a "struct list_head"
organization, which is IMHO cleaner.

Also renamed usb_cardp to cardp, as in the reset of the code.

Renamed reset_device() to if_usb_reset_device() like many other functions.

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>