clk: samsung: Remove meaningless __init and extern from header files

Remove useless __init atrribute and unneeded extern qualifier in function
declarations in header files.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20211015151425.29743-1-s.nawrocki@samsung.com