Convert CONFIG_TWL4030_USB to Kconfig

This converts the following to Kconfig:
   CONFIG_TWL4030_USB

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/nokia_rx51_defconfig b/configs/nokia_rx51_defconfig
index 570bb3f..e93042e 100644
--- a/configs/nokia_rx51_defconfig
+++ b/configs/nokia_rx51_defconfig
@@ -30,6 +30,7 @@
 CONFIG_USB_MUSB_HCD=y
 CONFIG_USB_MUSB_UDC=y
 CONFIG_USB_OMAP3=y
+CONFIG_TWL4030_USB=y
 CONFIG_VIDEO=y
 CONFIG_CFB_CONSOLE_ANSI=y
 # CONFIG_VGA_AS_SINGLE_DEVICE is not set