powerpc/powernv: Fix mis-merge of OPAL support for LEDS driver

When I merged the OPAL support for the powernv LEDS driver I missed a
hunk.

This is slightly modified from the original patch, as the original added
code to opal-api.h which is not in the skiboot version, which is
discouraged.

Instead those values are moved into the driver, which is the only place
they are used.

Fixes: 8a8d9181 ("powerpc/powernv: Add OPAL interfaces for accessing and modifying system LED states")
Reviewed-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>