dt-bindings: firmware: Add Open Profile for DICE

Add DeviceTree bindings for Open Profile for DICE. DICE is a protocol
for deriving Compound Device Identifier (CDI) certificates. These are
generated by the firmware/bootloader and stored in memory. Location of
the buffer is described as a reserved memory region referenced by
a compatible DICE device node.

See https://pigweed.googlesource.com/open-dice

Signed-off-by: David Brazdil <dbrazdil@google.com>