hostap: fix an error code in prism2_config()

The current code returns success if prism2_init_local_data() fails, but
we want to return an error code.  Also we can remove the bogus
ret initializer because it is wrong and never used.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>