Fix compile error related to r8a66597-hcd & usb

When building the 8544DS board we get this error:

In file included from r8a66597-hcd.c:22:
u-boot/include/usb.h:190:2: error: #error USB Lowlevel not defined
make[1]: *** [r8a66597-hcd.o] Error 1

The cleanest fix is to only build r8a66597-hcd.c if CONFIG_USB_R8A66597_HCD
is set.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

drivers/usb/Makefile

@@ -25,10 +25,11 @@ include $(TOPDIR)/config.mk
 
 LIB	:= $(obj)libusb.a
 
+COBJS-$(CONFIG_USB_R8A66597_HCD) += r8a66597-hcd.o
+
 COBJS-y += isp116x-hcd.o
 COBJS-y += sl811_usb.o
 COBJS-y += usb_ohci.o
-COBJS-y += r8a66597-hcd.o
 COBJS-y += usbdcore.o
 COBJS-y += usbdcore_ep0.o
 COBJS-y += usbdcore_mpc8xx.o

drivers/usb/r8a66597-hcd.c

@@ -24,8 +24,6 @@
 
 #include "r8a66597.h"
 
-#if defined(CONFIG_USB_R8A66597_HCD)
-
 #ifdef R8A66597_DEBUG
 #define R8A66597_DPRINT		printf
 #else
@@ -919,6 +917,3 @@ int usb_lowlevel_stop(void)
 
 	return 0;
 }
-
-#endif	/* CONFIG_USB_R8A66597_HCD */
-