arm: vt8500: clk: Add Common Clock Framework support

This patch adds common clock framework support for arch-vt8500.
Support for PLL and device clocks on VT8500, WM8505 and WM8650
are included.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Acked-by: Mike Turquette <mturquette@linaro.org>