[bug report] clk: mediatek: add missing cpu mux causing Mediatek cpufreq can't work

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Sean Wang,

The patch 1e17de9049da: "clk: mediatek: add missing cpu mux causing
Mediatek cpufreq can't work" from May 5, 2017, leads to the following
static checker warning:

	drivers/clk/mediatek/clk-cpumux.c:39 clk_cpumux_get_parent()
	warn: signedness bug returning '(-22)'

drivers/clk/mediatek/clk-cpumux.c
    27  static u8 clk_cpumux_get_parent(struct clk_hw *hw)
    28  {
    29          struct mtk_clk_cpumux *mux = to_mtk_clk_cpumux(hw);
    30          int num_parents = clk_hw_get_num_parents(hw);
    31          unsigned int val;
    32  
    33          regmap_read(mux->regmap, mux->reg, &val);
    34  
    35          val >>= mux->shift;
    36          val &= mux->mask;
    37  
    38          if (val >= num_parents)
    39                  return -EINVAL;
                        ^^^^^^^^^^^^^^
Doesn't work for u8.

    40  
    41          return val;
    42  }

regards,
dan carpenter