usb: kconfig: fix warning of select USB_OTG

usb: kconfig: fix warning of select USB_OTG

When choose randconfig for kernel build, it reports below warning:
"warning: (USB_OTG_FSM && FSL_USB2_OTG && USB_MV_OTG) selects USB_OTG
which has unmet direct dependencies (USB_SUPPORT && USB && PM)"

In fact, USB_OTG is visible symbol and depends on PM, so the driver
needs to depend on it to reduce dependency problem.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Cc: Felipe Balbi <balbi@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>