clk: bm1800: Remove set but not used variable 'fref'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/clk/clk-bm1880.c: In function 'bm1880_pll_rate_calc':
drivers/clk/clk-bm1880.c:477:13: warning:
 variable 'fref' set but not used [-Wunused-but-set-variable]

It is never used, so remove it.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lkml.kernel.org/r/20191129033534.188257-1-yuehaibing@huawei.comSigned-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk-bm1880.c

@@ -474,11 +474,10 @@ static struct bm1880_composite_clock bm1880_composite_clks[] = {
 static unsigned long bm1880_pll_rate_calc(u32 regval, unsigned long parent_rate)
 {
 	u64 numerator;
-	u32 fbdiv, fref, refdiv;
+	u32 fbdiv, refdiv;
 	u32 postdiv1, postdiv2, denominator;
 
 	fbdiv = (regval >> 16) & 0xfff;
-	fref = parent_rate;
 	refdiv = regval & 0x1f;
 	postdiv1 = (regval >> 8) & 0x7;
 	postdiv2 = (regval >> 12) & 0x7;