omap4: pandaboard: remove unused hsmmc definition

remove the second hsmmc definition as it is only used on the
expansion header of the PandaBoard and can be mux for other
functions.

Signed-off-by: David Anders <x0132446@ti.com>
Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>