ARM: at91/DT: at91sam9x5ek: fix USB host property to enable port C

ARM: at91/DT: at91sam9x5ek: fix USB host property to enable port C

Device Tree "num-ports" property of USB host node has to be
set to maximum number of ports available.
The possibility to activate a particular port is done by specifying the proper
gpio configuration for its vbus.

This patch fixes the USB host node by configuring the 3 ports available on the
product and letting "port A" available for USB gadget usage.

Reported-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Bo Shen <voice.shen@atmel.com>