Using Combo Event 0 to start trace module for VE2

[parthash0804]

Problem solved by the commit

As of now we were generating USER_EVENT_0 in CDO to start the trace module for VE2 which was interfering with two of the profiling metric sets.

Bug / issue (if any) fixed, which PR introduced the bug, how it was discovered

How problem was solved, alternative solutions (if any) and why they were rejected

After discussion with @pgschuey and @vipangul we decided to use combo_event_0 which is not being used currently and won't interfere with trace.

Risks (if any) associated the changes in the commit

Changes needs to be done in AIECompiler to start generating COMBO_EVENT_0 in cdo instead of USER_EVENT_0. Once this PR is merged @jyothees99 will submit the changes on compiler side. Once the compiler changes are in TA we can update the XRT submodule in VE2 to point to this commit.

What has been tested and how, request additional testing if necessary

Tested trace on eff_net design on both hardware and QEMU.

Documentation impact (if any)

NA

[pgschuey]

We are not currently using combo event 0, so this should be ok.