powerpc/perf: Cleanup cache_sel bits comment

Update the raw event code comment in power9-pmu.c with respect to
"cache" bits, since power9 MMCRC does not support these.
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/perf/power9-pmu.c

@@ -63,14 +63,6 @@
  *	MMCRA[9:11] = thresh_cmp[0:2]
  *	MMCRA[12:18] = thresh_cmp[3:9]
  *
- * if unit == 6 or unit == 7
- *	MMCRC[53:55] = cache_sel[1:3]      (L2EVENT_SEL)
- * else if unit == 8 or unit == 9:
- *	if cache_sel[0] == 0: # L3 bank
- *		MMCRC[47:49] = cache_sel[1:3]  (L3EVENT_SEL0)
- *	else if cache_sel[0] == 1:
- *		MMCRC[50:51] = cache_sel[2:3]  (L3EVENT_SEL1)
- * else if cache_sel[1]: # L1 event
  * MMCR1[16] = cache_sel[2]
  * MMCR1[17] = cache_sel[3]
  *