ARM: OMAP: Define use internal clock field in MMCconfiguration

With the recent omap24xx register cleanup, the CONTROL_DEVCONF is only defined
at arch/arm/mach-omap2/pm.c.
So define 24XX_CONTROL_DEVCONF and use internal clock field in MMC
configuration.
I think it's the proper place to set mmc clock instead of  board-specific one.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
--
b/arch/arm/mach-omap2/board-apollon.c
Signed-off-by: Tony Lindgren <tony@atomide.com>