mmc: sdhci-*: Don't emit error msg if sdhci_add_host() fails

I noticed below error msg with sdhci-pxav3 on some berlin platforms:

[.....] sdhci-pxav3 f7ab0000.sdhci failed to add host

It is due to getting related vmmc or vqmmc regulator returns
-EPROBE_DEFER. It doesn't matter at all but it's confusing.

>From another side, if driver probing fails and the error number isn't
-EPROBE_DEFER, the core will tell us something as below:

[.....] sdhci-pxav3: probe of f7ab0000.sdhci failed with error -EXX

So it's not necessary to emit error msg if sdhci_add_host() fails. And
some other sdhci host drivers also have this issue, let's fix them
together.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>