ARM: OMAP: Split plat/mmc.h into local headers and platform_data

We need to remove this from plat for ARM common zImage
support.

Also remove includes not needed by the omap_hsmmc.c driver.

Cc: linux-mmc@vger.kernel.org
Acked-by: Chris Ball <cjb@laptop.org>
Acked-by: Venkatraman S <svenkatr@ti.com>
[tony@atomide.com: fold in removal of unused driver includes]
Signed-off-by: Tony Lindgren <tony@atomide.com>