Kconfig: USB: Migrate CONFIG_USB_EHCI_HCD users to Kconfig

Migrate the rest of the users of CONFIG_USB_EHCI_HCD over to Kconfig.
For a few SoCs, imply or default y this if USB is enabled.  In some
cases we had not already migrated to CONFIG_USB so do that as well.

Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Marek Vasut <marex@denx.de>
diff --git a/configs/mpc5121ads_rev2_defconfig b/configs/mpc5121ads_rev2_defconfig
index ad46e02..e8f83bf 100644
--- a/configs/mpc5121ads_rev2_defconfig
+++ b/configs/mpc5121ads_rev2_defconfig
@@ -22,5 +22,6 @@
 CONFIG_MTD_NOR_FLASH=y
 # CONFIG_PCI is not set
 CONFIG_USB=y
+CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_STORAGE=y
 CONFIG_OF_LIBFDT=y