clk: prima2: fix return value check in sirfsoc_of_clk_init()

In case of error, the function clk_get() returns ERR_PTR()
not NULL. The NULL test in the return value check should
be replaced with IS_ERR().
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Barry Song <21cnbao@gmail.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
[mturquette@linaro.org: added missing parenthesis to fix compile break]

drivers/clk/clk-prima2.c

@@ -1113,7 +1113,7 @@ void __init sirfsoc_of_clk_init(void)
 
 	for (i = pll1; i < maxclk; i++) {
 		prima2_clks[i] = clk_register(NULL, prima2_clk_hw_array[i]);
-		BUG_ON(!prima2_clks[i]);
+		BUG_ON(IS_ERR(prima2_clks[i]));
 	}
 	clk_register_clkdev(prima2_clks[cpu], NULL, "cpu");
 	clk_register_clkdev(prima2_clks[io],  NULL, "io");