usb: musb: remove all 'select' from Kconfig

those are quite unnecessary, the only thing
we need to be careful about is USB_OTG_UTILS
which get properly selected by PHY drivers.

For now, MUSB will select only USB_OTG_UTILS
until we add stubs for the cases when PHY
layer isn't enabled.

Signed-off-by: Felipe Balbi <balbi@ti.com>