drm/amdkfd: Replace deprecated gfx12 trap handler instructions

Newer assemblers reject S_WAITCNT. All instances of S_WAITCNT can be
replaced by S_WAITCNT 0 (< gfx12) or S_WAIT_IDLE (>= gfx12) since
there is no concurrency of different memory instruction classes.

Signed-off-by: Jay Cornwall <jay.cornwall@amd.com>
Reviewed-by: Lancelot Six <lancelot.six@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>