USB: g_file_storage: automatically disable stalls under Atmel

This patch (as1220) automatically disables stalls when g_file_storage
finds itself running with an Atmel device controller, because the
Atmel hardware/driver isn't capable of halting bulk endpoints
correctly.

Reported-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>