So to do an efi install you had to go into the PC UEFI setup and select the hybrid efi boot from the openSUSE DVD boot disk and with 12.3 I remember it only worked from the DVD ISO though I am not as sure about tat on13.1, but its what I would do now as well.
I would like to add for a hard disk smaller than 2.2 GB there is no compelling reason to use an efi boot for an openSUSE only system which just creates problems. You can create a new openSUSE 13.1 rescue disk where you can execute the instructions to convert a gpt disk into a normal MBR disk which you can find on the internet.
You should backup your /home partition to something external like an external hard drive or thumb drive before you convert the drive to MBR. If you do this your life using openSUSE will be much simpler from now on.