clk: mediatek: fixed static checker warning in clk_cpumux_get_parent call

Fixed the signedness bug returning '(-22)' on the return type as u8 with
removing the sanity checker in clk_cpumux_get_parent() since
clk_cpumux_set_parent() always ensures validity in clk_cpumux_get_parent()
got called.

Fixes: 1e17de9049da ("clk: mediatek: add missing cpu mux causing Mediatek cpufreq can't work")
Reported-by: Dan Carpenter <[e-mail]>
Signed-off-by: Sean Wang <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/mediatek/clk-cpumux.c

···
 static u8 clk_cpumux_get_parent(struct clk_hw *hw)
 {
 	struct mtk_clk_cpumux *mux = to_mtk_clk_cpumux(hw);
-	int num_parents = clk_hw_get_num_parents(hw);
 	unsigned int val;
 
 	regmap_read(mux->regmap, mux->reg, &val);
 
 	val >>= mux->shift;
 	val &= mux->mask;
-
-	if (val >= num_parents)
-		return -EINVAL;
 
 	return val;
 }