driver-core: firmware_class: remove base.h header inclusion

base.h is used by base drivers for sharing internal structures.
Turns out firmware_class does not depend on it at all so remove it.

Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>