MAINTAINERS: Add TI OMAP SDHCI Maintainer

Add Maintainer for the TI OMAP SDHCI driver.

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>