Always build EC xlator

Now EC xlator does not require MMX anymore, always build it.

BUG: 764655
Change-Id: I50a64e22c080f2759eaa57786e7f69c34f11f89c
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/8451
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Harshavardhana <harsha@harshavardhana.net>
Tested-by: Harshavardhana <harsha@harshavardhana.net>