Clean up: remove unnecessary display info access

The previous fixes changed the calculation to use the display related
information from the context to make things consistent. The display info
is no longer needed.

Additional comments are added to clarify that the context should be the
display context containing the corresponding cutout to avoid misuse.

Bug: 404727504
Test: build
Flag: EXEMPT cleanup
Change-Id: I3d32c57d4c1938da390aefc493d532c4fd6ef101