MIPS: BMIPS: select CPU_HAS_PREFETCH

As they are MIPS32 CPUs they do support the prefetch opcode.
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6243/

arch/mips/Kconfig

@@ -1393,6 +1393,7 @@ config CPU_BMIPS
 	select SWAP_IO_SPACE
 	select WEAK_ORDERING
 	select CPU_SUPPORTS_HIGHMEM
+	select CPU_HAS_PREFETCH
 	help
 	  Support for BMIPS3300/4350/4380 and BMIPS5000 processors.