This commits extends etnaviv_gpu_cmdbuf_new(..) to define the number
of struct etnaviv_perfmon elements gets used.

Changes from v1 -> v2:
- make use of goto as requested by Lucas
Signed-off-by: NChristian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: NLucas Stach <l.stach@pengutronix.de>