Add bindings for ACLK_CPU, HCLK_CPU, PCLK_CPU, ACLK_PERI, HCLK_PERI, PCLK_PERI.

We need this to init it's rate at boot time.
Signed-off-by: Paweł Jarosz <paweljarosz3691@gmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>