dts: bindings: clocks: Add binding for F4 PLL I2S

Provide dts binding for F4 PLL I2S.
This PLL share input source and input M diviso with F4 Main PLL.

Only one output clock (PLLR) is supported for now.
This PLL could be found on STM32F401 parts for instance.

Additionally, provide related header definitions.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>