Rename SPL_USB_HOST_SUPPORT to SPL_USB_HOST

Rename this option so that CONFIG_IS_ENABLED can be used with it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/pico-imx6_defconfig b/configs/pico-imx6_defconfig
index 3193295..1eb82c1 100644
--- a/configs/pico-imx6_defconfig
+++ b/configs/pico-imx6_defconfig
@@ -28,7 +28,7 @@
 CONFIG_SPL_SEPARATE_BSS=y
 CONFIG_SPL_FIT_IMAGE_TINY=y
 CONFIG_SPL_FS_EXT4=y
-CONFIG_SPL_USB_HOST_SUPPORT=y
+CONFIG_SPL_USB_HOST=y
 CONFIG_SPL_USB_GADGET=y
 CONFIG_SPL_USB_SDP_SUPPORT=y
 CONFIG_SPL_WATCHDOG=y