coresight-tmc-etr: Remove irrelevant conditional logic

As part of the change to add scatter gather support  memory
assignment is being handled by mem alloc function. This change
gets rid of the old conditional logic which became irrelevant
since memory assignment has changed. The code being removed does not
have any effect on execution path.

Change-Id: Ib0628a9b024e911e4400a03af1f98fd1c12c92a7
Signed-off-by: Satyajit Desai <sadesai@codeaurora.org>