Convert CONFIG_USB_MUSB_OMAP2PLUS et al to Kconfig

This converts the following to Kconfig:
   CONFIG_USB_MUSB_OMAP2PLUS
   CONFIG_USB_MUSB_AM35X
   CONFIG_USB_MUSB_DSPS
   CONFIG_USB_MUSB_PIO_ONLY

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/cm_t3517_defconfig b/configs/cm_t3517_defconfig
index 819a95b..fa78bde 100644
--- a/configs/cm_t3517_defconfig
+++ b/configs/cm_t3517_defconfig
@@ -48,6 +48,7 @@
 CONFIG_OMAP3_SPI=y
 CONFIG_USB=y
 CONFIG_USB_MUSB_HOST=y
+CONFIG_USB_MUSB_AM35X=y
 CONFIG_USB_STORAGE=y
 CONFIG_LCD=y
 CONFIG_OF_LIBFDT=y