Return error when error occurs in buffer allocation.

Previously, the allocate buffer does not return error if it runs out of
memory. This change adds the error in returned status.

Test: buffer_hub_queue-test passes on Vega on oc-dr1-daydream-dev
branch.
Test: build and visually check on Vega on oc-dr1-daydream-dev branch.
Test: buffer_hub_queue-test passes on Marlin on master branch.

Change-Id: Ie226e506ff47d122cd4eef6071b44abedcd4be56