Convert CONFIG_CMD_FUSE to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_FUSE

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/mx51evk_defconfig b/configs/mx51evk_defconfig
index d7e5404..3f57c88 100644
--- a/configs/mx51evk_defconfig
+++ b/configs/mx51evk_defconfig
@@ -14,6 +14,7 @@
 CONFIG_CMD_MMC=y
 CONFIG_CMD_SPI=y
 CONFIG_CMD_USB=y
+CONFIG_CMD_FUSE=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_DHCP=y
 CONFIG_CMD_MII=y