mmc: sdhci-esdhc-imx: Manage sdhci_runtime_suspend_host error code

We need to return in case of error even if the actual implementation
of sdhci_runtime_suspend_host always return 0. We don't want to
power down the clock and the assuption is that the sdhci_runtime_suspend_host
always let the system consistent in case of failure

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>