DPE: Add index field to layer_context_t

Both layer_ctx and layer_idx are used throughout and passed
as input to various functions. Add index field to the
layer_ctx so that only pointer to context is required
to pass and implementation stays consistent.

Signed-off-by: Maulik Patel <maulik.patel@arm.com>
Change-Id: I1603c82ef1c11d558e7f0bafecb1e2eecfe09885
4 files changed