The services actually provided by the system controller are not
documented so add some words about what the system controller can
actually do. Add a link to the oneline documentation with the specific
details of each individual service.
Also, drop the unneeded label from the example.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>