Convert CONFIG_SPL_MUSB_NEW_SUPPORT to Kconfig

Move this option to Kconfig and tidy up existing uses.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/birdland_bav335b_defconfig b/configs/birdland_bav335b_defconfig
index 354857d..f6703e4 100644
--- a/configs/birdland_bav335b_defconfig
+++ b/configs/birdland_bav335b_defconfig
@@ -13,6 +13,7 @@
 CONFIG_SYS_EXTRA_OPTIONS="SERIAL1,CONS_INDEX=1"
 CONFIG_VERSION_VARIABLE=y
 CONFIG_SPL=y
+CONFIG_SPL_MUSB_NEW_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set