Update dt-binding document for pinctrl of Amlogic A9.
In Amlogic A9 SoC, a bank mux register reuse other banks.
The multiplexed part requires special processing and is
therefore incompatible with the previous SoCs.
Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>