Fix GraphicsMapperStableCTests#LockUnlockNoCPUUsage

Add CPU usage into buffer descriptions for 2 reasons:
- minigbm doesn't support allocating buffers with usage == 0
- it could happen that the allocation is not cpu-mappable in the fist
  place and this woiuld make  the test to pass by accident

Cherry-pick'ed from ag/30113001

Bug: b/374004471
Bug: b/384527749
Test: vts -m VtsHalGraphicsMapperStableC_TargetTest
Change-Id: I589e7673236107b92d3d6a2587eab55f81b8520d
Merged-In: I589e7673236107b92d3d6a2587eab55f81b8520d