soc: qcom: secure_buffer: Remove support for VMID_TRUSTED_UI

The VMID for the trusted VM is not known up-front. Thus, there
is no point in exposing VMID_TRUSTED_UI, so remove it. Callers of
hyp assign must use the resource manager APIs to deduce the VMID,
and pass it to the hyp assign call.

Change-Id: I93e2812abffd99bb5b42b7fccead91becc5015fd
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>