kernel: add missing config symbol

Signed-off-by: Felix Fietkau <[email protected]>

target/linux/generic/config-3.18

@@ -4216,6 +4216,7 @@ CONFIG_USB_GADGET_VBUS_DRAW=2
 # CONFIG_USB_MUSB_HDRC is not set
 # CONFIG_USB_MV_U3D is not set
 # CONFIG_USB_MV_UDC is not set
+# CONFIG_USB_MXS_PHY is not set
 # CONFIG_USB_NET2272 is not set
 # CONFIG_USB_NET2280 is not set
 # CONFIG_USB_NET_AX88179_178A is not set

target/linux/generic/config-4.1

@@ -4388,6 +4388,7 @@ CONFIG_USB_GADGET_VBUS_DRAW=2
 # CONFIG_USB_MUSB_HDRC is not set
 # CONFIG_USB_MV_U3D is not set
 # CONFIG_USB_MV_UDC is not set
+# CONFIG_USB_MXS_PHY is not set
 # CONFIG_USB_NET2272 is not set
 # CONFIG_USB_NET2280 is not set
 # CONFIG_USB_NET_AX88179_178A is not set

target/linux/generic/config-4.4

@@ -4422,6 +4422,7 @@ CONFIG_USB_GADGET_VBUS_DRAW=2
 # CONFIG_USB_MUSB_HDRC is not set
 # CONFIG_USB_MV_U3D is not set
 # CONFIG_USB_MV_UDC is not set
+# CONFIG_USB_MXS_PHY is not set
 # CONFIG_USB_NET2272 is not set
 # CONFIG_USB_NET2280 is not set
 # CONFIG_USB_NET_AX88179_178A is not set