sniper: Fastboot support

This adds support for the fastboot USB gadget, including flashing to the
internal MMC and reboot to bootloader or not.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Tom Rini <trini@konsulko.com>
[trini: Update to use Kconfig for MUSB]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/sniper_defconfig b/configs/sniper_defconfig
index d2e10a9..44cf359 100644
--- a/configs/sniper_defconfig
+++ b/configs/sniper_defconfig
@@ -5,3 +5,5 @@
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_FPGA is not set
+CONFIG_USB=y
+CONFIG_USB_MUSB_GADGET=y