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/brxre1_defconfig b/configs/brxre1_defconfig
index 0c2d7ed..15245dc 100644
--- a/configs/brxre1_defconfig
+++ b/configs/brxre1_defconfig
@@ -56,6 +56,7 @@
 CONFIG_SYS_NS16550=y
 CONFIG_USB=y
 CONFIG_USB_MUSB_HOST=y
+CONFIG_USB_MUSB_DSPS=y
 CONFIG_USB_STORAGE=y
 CONFIG_SYS_WHITE_ON_BLACK=y
 CONFIG_LCD=y