OMAPDSS: remove wrong HDMI HPD muxing

"hdmi_hpd" pin is muxed to INPUT and PULLUP, but the pin is not
currently used, and in the future when it is used, the pin is used as a
GPIO and is board specific, not an OMAP4 wide thing.

So remove the muxing for now.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>