mmc: sdhci-omap: Add sdhci_omap specific ops for enable_sdio_irq

Add sdhci_omap_enable_sdio_irq to set CTPL and CLKEXTFREE bits in
MMCHS_CON register required to detect asynchronous card interrupt
on DAT[1].

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>