cpupower: Don't fetch maximum latency when EPP is enabled

When EPP has been enabled the hardware will autonomously change
frequencies on it's own and thus there is no latency with changing
from the kernel.

Avoid doing the maximum latency check when EPP is found. This will
apply to both amd-pstate and intel-pstate drivers.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mario Limonciello <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>

Author: superm1

tools/power/cpupower/utils/cpufreq-info.c

@@ -445,6 +445,9 @@ static int get_latency(unsigned int cpu, unsigned int human)
 {
 	unsigned long latency = cpufreq_get_transition_latency(cpu);
 
+	if (!get_epp(cpu, false))
+		return -EINVAL;
+
 	printf(_("  maximum transition latency: "));
 	if (!latency || latency == UINT_MAX) {
 		printf(_(" Cannot determine or is not supported.\n"));