configs/linux: Use ondemand governor by default

So we don't run CPUs at full frequency while idle in petitboot.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
diff --git a/openpower/configs/linux/skiroot_defconfig b/openpower/configs/linux/skiroot_defconfig
index e54be62..78a02c0 100644
--- a/openpower/configs/linux/skiroot_defconfig
+++ b/openpower/configs/linux/skiroot_defconfig
@@ -29,6 +29,7 @@
 CONFIG_MODULE_UNLOAD=y
 CONFIG_PARTITION_ADVANCED=y
 # CONFIG_PPC_PMAC is not set
+CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y
 CONFIG_HZ_100=y
 CONFIG_KEXEC=y
 CONFIG_IRQ_ALL_CPUS=y