sparc: Don't do expensive hypervisor PCR write unless necessary.

The hypervisor call is only necessary if hypervisor events are
being requested.

So if we're not tracking hypervisor events, simply do a direct
register write.

Signed-off-by: David S. Miller <[e-mail]>

arch/sparc/kernel/pcr.c

···
 {
 	unsigned long ret;
 
-	ret = sun4v_niagara2_setperf(HV_N2_PERF_SPARC_CTL, val);
-	if (ret != HV_EOK)
+	if (val & PCR_N2_HTRACE) {
+		ret = sun4v_niagara2_setperf(HV_N2_PERF_SPARC_CTL, val);
+		if (ret != HV_EOK)
+			write_pcr(val);
+	} else
 		write_pcr(val);
 }