mmc: sdhci-msm: Warn about overclocking SD/MMC

mmc: sdhci-msm: Warn about overclocking SD/MMC

As talked about in commit 5e4b7e82d497 ("clk: qcom: gcc-sdm845: Use
floor ops for sdcc clks"), most clocks handled by the Qualcomm clock
drivers are rounded _up_ by default instead of down.  We should make
sure SD/MMC clocks are always rounded down in the clock drivers.
Let's add a warning in the Qualcomm SDHCI driver to help catch the
problem.

This would have saved a bunch of time [1].

NOTE: this doesn't actually fix any problems, it just makes it obvious
to devs that there is a problem and that should be an indication to
fix the clock driver.

[1] http://lore.kernel.org/r/20201210102234.1.I096779f219625148900fc984dd0084ed1ba87c7f@changeid

Suggested-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20201214092048.v5.1.Iec3430c7d3c2a29262695edef7b82a14aaa567e5@changeid
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>