feat(rdfremont): add dts files to enable hafnium as bl32

On RDFremont platform, Hafnium is used as SPMC running at SEL2 and
manage SP running at SEL0. Hafnium is loaded and configured as BL32
image. SP is loaded by SP load framework and configured by Hafnium.

Add the dts files needed to enable load and configuration of hafnium and
SP.

Signed-off-by: Nishant Sharma <nishant.sharma@arm.com>