clk/samsung: Use CLK_OF_DECLARE_DRIVER initialization method for CLKOUT

The Exynos PMU node is an interrupt, clock and PMU (Power Management Unit)
controller, and these functionalities are supported by different drivers
that matches the same compatible strings.

Since commit 989eafd0b609 ("clk: core: Avoid double initialization of
clocks") the OF core flags clock controllers registered with the
CLK_OF_DECLARE() macro as OF_POPULATED, so platform devices with the same
compatible string will not be registered.

This prevents the PMU platform device to be created, so the Exynos PMU
driver is never probed. This breaks (among other things) Suspend-to-RAM.

Fix this by changing CLKOUT driver initialization method to
CLK_OF_DECLARE_DRIVER(), which doesn't clear the OF_POPULATED flag, so
later a platform device is created and the Exynos PMU platform driver
can be be probed properly.

Fixes: 989eafd0b609 ("clk: core: Avoid double initialization of clocks")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>