clk: rockchip: fix mmc get phase

If the mmc clock has no rate, it can be assumed to be constant.
In such case, there is no measurable phase shift. Just return 0
in this case instead of returning an error.

Fixes: 27608786 ("clk: Bail out when calculating phase fails during clk registration")
Tested-by: Markus Reichl <m.reichl@fivetechno.de>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lkml.kernel.org/r/20200303192956.64410-1-jbrunet@baylibre.comSigned-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/rockchip/clk-mmc-phase.c

@@ -51,9 +51,9 @@ static int rockchip_mmc_get_phase(struct clk_hw *hw)
 	u16 degrees;
 	u32 delay_num = 0;
 
-	/* See the comment for rockchip_mmc_set_phase below */
+	/* Constant signal, no measurable phase shift */
 	if (!rate)
-		return -EINVAL;
+		return 0;
 
 	raw_value = readl(mmc_clock->reg) >> (mmc_clock->shift);