[Blackfin] arch: protect linux/usb/musb.h include until the driver gets mainlined

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

arch/blackfin/mach-bf548/boards/cm_bf548.c

@@ -36,7 +36,9 @@
 #include <linux/spi/flash.h>
 #include <linux/irq.h>
 #include <linux/interrupt.h>
+#if defined(CONFIG_USB_MUSB_HDRC) || defined(CONFIG_USB_MUSB_HDRC_MODULE)
 #include <linux/usb/musb.h>
+#endif
 #include <asm/bfin5xx_spi.h>
 #include <asm/cplb.h>
 #include <asm/dma.h>