mmc: sdhci-iproc: Clean up platform allocations if shdci init fails

This patch adopts the changes from 475c9e43 ("mmc: sdhci-bcm2835:
Clean up platform allocations if sdhci init fails") to sdhci-iproc.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>