clk: x86: Add ST oscout platform clock

Stoney SoC provides oscout clock. This clock can support 25Mhz and
48Mhz of frequency.
The clock is available for general system use.

Signed-off-by: Akshu Agrawal <akshu.agrawal@amd.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>