Revert "slim_msm: support non-blocking writes from slimbus MSM controller"

 * I'm seeing overflows after applying this patch. Reverting for now.

This reverts commit 8f1aef70167f72a403a7e2e8840b2c09d6bf82a3.

Change-Id: I5a3972ac68d619f7cb7ce81f4f25f80350461ab7