clk: samsung: Remove dead code

samsung_clk_register_pll2550x() function is not used anymore,
so remove its declaration.
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: NKrzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: NSylwester Nawrocki <s.nawrocki@samsung.com>

drivers/clk/samsung/clk-pll.h

@@ -103,8 +103,4 @@ struct samsung_pll_rate_table {
 	unsigned int vsel;
 };
 
-extern struct clk * __init samsung_clk_register_pll2550x(const char *name,
-			const char *pname, const void __iomem *reg_base,
-			const unsigned long offset);
-
 #endif /* __SAMSUNG_CLK_PLL_H */