lisa.trace: De-hardcode tracefs location
FIX
Detect tracefs location automatically.
relies on devlib PR: https://github.com/ARM-software/devlib/pull/590
LISA branch that comes with the devlib change as well for testing:
remote:
The devlib PR is merged and subtree in lisa repo updated, so this PR can be used directlyhttps://github.com/douglas-raillard-arm/lisa.git
branch: detect_tracefs