config: compile USB controllers as modules

This makes possible to not attach the device there before pciback takes
them.

config

@@ -4812,12 +4812,12 @@ CONFIG_USB_WUSB_CBAF=m
 # USB Host Controller Drivers
 #
 # CONFIG_USB_C67X00_HCD is not set
-CONFIG_USB_XHCI_HCD=y
-CONFIG_USB_XHCI_PCI=y
-CONFIG_USB_EHCI_HCD=y
+CONFIG_USB_XHCI_HCD=m
+CONFIG_USB_XHCI_PCI=m
+CONFIG_USB_EHCI_HCD=m
 CONFIG_USB_EHCI_ROOT_HUB_TT=y
 CONFIG_USB_EHCI_TT_NEWSCHED=y
-CONFIG_USB_EHCI_PCI=y
+CONFIG_USB_EHCI_PCI=m
 CONFIG_USB_EHCI_HCD_PLATFORM=m
 # CONFIG_USB_OXU210HP_HCD is not set
 # CONFIG_USB_ISP116X_HCD is not set
@@ -4825,10 +4825,11 @@ CONFIG_USB_EHCI_HCD_PLATFORM=m
 CONFIG_USB_ISP1362_HCD=m
 CONFIG_USB_FUSBH200_HCD=m
 # CONFIG_USB_FOTG210_HCD is not set
-CONFIG_USB_OHCI_HCD=y
-CONFIG_USB_OHCI_HCD_PCI=y
+CONFIG_USB_OHCI_HCD=m
+CONFIG_USB_OHCI_HCD_PCI=m
+# CONFIG_USB_OHCI_HCD_SSB is not set
 CONFIG_USB_OHCI_HCD_PLATFORM=m
-CONFIG_USB_UHCI_HCD=y
+CONFIG_USB_UHCI_HCD=m
 CONFIG_USB_U132_HCD=m
 CONFIG_USB_SL811_HCD=m
 CONFIG_USB_SL811_HCD_ISO=y