coresight: improve error handling for exported coresight apis

Enhance error handling to provide graceful behavior in the case
of incorrect topology representation by the user. This
specifically improves the behavior when some of the required
device DT nodes are missed or required driver(s) are not
compiled.

CRs-Fixed: 446155
Change-Id: I1bb72732a6f2d230775d8ce1ffec574adc3890d0
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>