config: Add support to run optee in SEL1 with no FF-A or SEL2/Hafnium

This is base configuration to run OPTEE in the secure world. It doesn't
include any FF-A or S-EL2/Hafnium. This is useful to compare it with
other configurations that include FF-A and/or Hafnium in S-EL2.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>