MIPS: OCTEON: Fix USB platform code breakage.

Fix build error when CONFIG_SMP is turned off:

CC [M]  arch/mips/cavium-octeon/octeon-usb.o
arch/mips/cavium-octeon/octeon-usb.c: In function
‘dwc3_octeon_device_init’:
arch/mips/cavium-octeon/octeon-usb.c:540:4: error: implicit declaration
of function ‘devm_iounmap’ [-Werror=implicit-function-declaration]
     devm_iounmap(&pdev->dev, base);

Signed-off-by: Steven J. Hill <steven.hill@cavium.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Tested-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16907/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/cavium-octeon/octeon-usb.c

@@ -13,9 +13,9 @@
 #include <linux/mutex.h>
 #include <linux/delay.h>
 #include <linux/of_platform.h>
+#include <linux/io.h>
 
 #include <asm/octeon/octeon.h>
-#include <asm/octeon/cvmx-gpio-defs.h>
 
 /* USB Control Register */
 union cvm_usbdrd_uctl_ctl {