clk: exynos5440: move restart code into clock driver

Let's register restart handler for Exynos5440 from it's clock driver
for restart functionality. So that we can cleanup restart hooks from
machine specific file.

CC: Sylwester Nawrocki <s.nawrocki@samsung.com>
CC: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>