Update the documentation to support clock driver for the Amlogic SM1 SoC
and expose the GP1, DSU and the CPU 1, 2 & 3 clocks.

SM1 clock tree is very close, the main differences are :
- each CPU core can achieve a different frequency, albeit a common PLL
- a similar tree as the clock tree has been added for the DynamIQ Shared
  Unit
- has a new GP1 PLL used for the DynamIQ Shared Unit
- SM1 has additional clocks like for CSI, NanoQ an other components
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>