coresight-ost: switch to no log api for STM device writes

write_relaxed apis have an overhead of doing RTB logging. This
results in slow down of STM device because of the number of device
writes that need to be performed. Move over to the no logging
variants of the apis.

Change-Id: If7ebae48a56a80d5de556171aff6feb4564ee61a
Signed-off-by: Satyajit Desai <sadesai@codeaurora.org>