drm/msm/dpu: Track resources in global state

Move mapping of resources to encoder ids from the resource manager to a
new dpu_global_state struct. Store this struct in global atomic state.

Before this patch, atomic test would be performed by modifying global
state (resource manager), and backing out any changes if the test fails.
By using drm atomic global state, this is not necessary as any changes
to the global state will be discarded if the test fails.

Signed-off-by: Drew Davenport <ddavenport@chromium.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>