ARM: OMAP5: set mmc clock frequency to 192MHz

Now that omap_hsmmc has support for hs200 mode, change the clock
frequency to 192MHz. Also change the REFERENCE CLOCK frequency to
192MHz based on which the internal mmc clock divider is calculated.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>