coresight: add checks to avoid crash for coresight fuse

Add more checks for coresight fuse driver to avoid device crash
when coresight fuse driver is enabled but dt node is missing.

Change-Id: Ib18feec45ec81ae4aa64b94e1691364fea56a826
Signed-off-by: Xiaogang Cui <xiaogang@codeaurora.org>