USB: g_file_storage: ignore bulk-out data after invalid CBW

This patch (as1061) makes g_file_storage more compliant with the
Bulk-Only Transport specification.  After an invalid CBW is received,
the gadget must ignore any further bulk-OUT data until it is reset.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>