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/sniper_defconfig b/configs/sniper_defconfig
index a8a592f..c75b1ba 100644
--- a/configs/sniper_defconfig
+++ b/configs/sniper_defconfig
@@ -39,6 +39,7 @@
 CONFIG_SYS_NS16550=y
 CONFIG_USB=y
 CONFIG_USB_MUSB_GADGET=y
+CONFIG_USB_MUSB_OMAP2PLUS=y
 CONFIG_USB_GADGET=y
 CONFIG_USB_GADGET_MANUFACTURER="Texas Instruments"
 CONFIG_USB_GADGET_VENDOR_NUM=0x0451