[MIPS] Include cacheflush.h in uncache.c

This fixes this sparse warning:

arch/mips/lib/uncached.c:38:22: warning: symbol 'run_uncached' was not declared. Should it be static?
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/lib/uncached.c

@@ -12,6 +12,7 @@
 
 #include <asm/addrspace.h>
 #include <asm/bug.h>
+#include <asm/cacheflush.h>
 
 #ifndef CKSEG2
 #define CKSEG2 CKSSEG