mmc: sdhci-imx-esdhc: use more devm_* functions

Use devm_kzalloc, devm_gpio_request_one and devm_request_irq to make
cleanup path simpler.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>