usb: gadget: drop "select USB_GADGET_S3C_HSOTG_PIO"

There is no Kconfig symbol named USB_GADGET_S3C_HSOTG_PIO. The select
statement for that symbol is a nop. Drop it.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>