clk: samsung: add pll clock registration helper functions

There are several types of pll clocks used in Samsung SoC's and these
pll clocks can be represented as Samsung specific pll clock types and
registered with the common clock framework. Add support for pll35xx,
pll36xx, pll45xx, pll46xx and pll2550x clock types and helper functions
to register them.

Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Tested-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Tested-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>