dmfe: fix two bugs

Fix a oops on module removal due to deallocating memory before unregistring
driver Fix a NULL pointer dereference when dev_alloc_skb fails

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Cc: Valerie Henson <val_henson@linux.intel.com>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>