MIPS: bmips: Fix compiler warning observed on W=1 build

The function arch_sync_dma_for_cpu_all() was used but was
missing a prototype declaration.

Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/bmips/dma.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0+
 
 #include <linux/types.h>
+#include <linux/dma-map-ops.h>
 #include <asm/bmips.h>
 #include <asm/io.h>