powerpc/85xx: enable USB2 gadget mode for corenet ds board

to make USB2 worked in gadget mode, we need to set it's 'dr_mode' to
'peripheral' in hwconfig, but driver starts scan from 'usb1', it'll break
out if it cannot find 'usb1', so drop the 'else' clause to make driver scan
all the 'usbx'.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>