clk: meson: use the frac parameter width instead of a constant

Use the fractional part width in the calculation instead of 12, which
happens to be the witdh right now. This is safer in case the field width
ever change in the future

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>

drivers/clk/meson/clk-pll.c

@@ -81,7 +81,7 @@ static unsigned long meson_clk_pll_recalc_rate(struct clk_hw *hw,
 		reg = readl(pll->base + p->reg_off);
 		frac = PARM_GET(p->width, p->shift, reg);
 
-		rate += mul_u64_u32_shr(parent_rate, frac, 12);
+		rate += mul_u64_u32_shr(parent_rate, frac, p->width);
 		rate *= 2;
 	}