Removing "shiftID" from BackendProfilingCounterRegisterMockBackendTest

This test case has caused several problems over the years. All the
problems are around using counter indices to identify counters rather
than names. Updating the test to check for registered counter names.

Signed-off-by: Nikhil Raj <nikhil.raj@arm.com>
Signed-off-by: Colm Donelan <colm.donelan@arm.com>
Change-Id: Ic5ebc9b2d53f2db301a3067ecce4befc14dcb8a5