Revert "sdm: Allocate layer stack objects individually."

This reverts commit 66b1fa541b3f28d02940b6a93316dc8b449f81ae.
This commit did not fix layer stack corruption. This commit
caused frequent memory allocation/deallocations.

CRs-Fixed: 982059

Change-Id: I80d295b7acf8637446ee644f94397b532f373b4b
2 files changed