clk: parent_names should be const ...

Not only the array of pointers should be const, but also the strings
they point to. Add missing const.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

clk: clk-composite: return parent_rate if no rate clk ...

When a composite clock has no rate clock then it should output the
parents rate.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

CLK: Add support for composite clock from Linux kernel ...

Signed-off-by: Andrey Panov <rockford@yandex.ru>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>