usb: common: Weed out USB_**_PRINTFs from usb framework

USB_PRINTF, USB_HUB_PRINTF, USB_STOR_PRINTF, USB_KBD_PRINTF
are nothing but conditional debug prints, depending on DEBUG.
So better remove them and use debug() simply.

Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>