coresight: remove NULL check from drivers

Remove NULL checks for pdev->dev.of_node from CoreSight drivers
altogether. It is safe to remove this NULL check since all the
of_* family of functions used within CoreSight drivers internally
call __of_find_property() which checks for this NULL pointer
anyway.

Change-Id: I7696c596c11d6fc2a0397fb2a1ccfc0bfbffcd52
Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>