acenic: Pass up error code from ace_load_firmware()

If ace_load_firmware() fails, ace_init() cleans up but still returns
0, leading to an oops as seen in <http://bugs.debian.org/521383

>.
It should pass the error code up.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>