powerpc/powernv: Enable LEDS support

Commit 84ad6e5c added LEDS support for PowerNV platform. Lets
update ppc64_defconfig to pick LEDS driver.

PowerNV LEDS driver looks for "/ibm,opal/leds" node in device
tree and loads if this node exists. Hence added it as 'm'.

Also note that powernv LEDS driver needs NEW_LEDS and LEDS_CLASS
as well. Hence added them to config file.

mpe: Also add them to pseries_defconfig, which is currently also used
for powernv systems.

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>