To support multipass, querying perf counters happens in several steps
below.

0) There's a scratch reg to set pass indices for perf counters query.
   Prepare cmd streams to set each pass index to the reg at device
   creation time. See tu_CreateDevice in tu_device.c
1) Emit command streams to read all requested perf counters at all
   passes in begin/end query with CP_REG_TEST/CP_COND_REG_EXEC, which
   reads the scratch reg where pass index is set.
2) Pick the right cs setting proper pass index to the reg and prepend it
   to the command buffer at each submit time.
3) If the pass index in the reg is true, then executes the command
   stream below CP_COND_REG_EXEC.

Would need to implement for kgsl in the future.

Signed-off-by: Hyunjun Ko <zzoon@igalia.com>
Part-of: <!6808>