[PATCH] hostap: Remove dead code (duplicated idx != 0)

The Coverity checker (CID: 58) spotted this duplicated idx != 0
validation for unicast keys in prism2_ioctl_siwencodeext().

Signed-off-by: Jouni Malinen <jkmaline@cc.hut.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>