usb: s/CONFIG_DM_USB/CONFIG_IS_ENABLED(DM_USB)/

This allows to disable the USB driver model in SPL because it checks
the CONFIG_SPL_DM_USB variable for SPL builds. Nothing changes for
regular non-SPL builds.

Signed-off-by: Sven Schwermer <sven@svenschwermer.de>
diff --git a/drivers/usb/host/ohci.h b/drivers/usb/host/ohci.h
index fba78dc..f9f02cb 100644
--- a/drivers/usb/host/ohci.h
+++ b/drivers/usb/host/ohci.h
@@ -27,7 +27,7 @@
 #define ED_ALIGNMENT 16
 #endif
 
-#if defined CONFIG_DM_USB && ARCH_DMA_MINALIGN > 32
+#if CONFIG_IS_ENABLED(DM_USB) && ARCH_DMA_MINALIGN > 32
 #define TD_ALIGNMENT ARCH_DMA_MINALIGN
 #else
 #define TD_ALIGNMENT 32
@@ -406,7 +406,7 @@
 	const char	*slot_name;
 } ohci_t;
 
-#ifdef CONFIG_DM_USB
+#if CONFIG_IS_ENABLED(DM_USB)
 extern struct dm_usb_ops ohci_usb_ops;
 
 int ohci_register(struct udevice *dev, struct ohci_regs *regs);