Blackfin: add new cacheflush syscall

Flushing caches sometimes requires anomaly workarounds which require
supervisor-only insns.  Normally we don't need to flush caches from
userspace so this isn't a problem, but when gcc generates trampolines
on the stack, we do.

So add a new syscall for gcc to use modeled after the mips version.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/include/asm/Kbuild b/arch/blackfin/include/asm/Kbuild
index d9eb29e..9e7c537 100644
--- a/arch/blackfin/include/asm/Kbuild
+++ b/arch/blackfin/include/asm/Kbuild
@@ -1,4 +1,5 @@
 include include/asm-generic/Kbuild.asm
 
 header-y += bfin_sport.h
+header-y += cachectl.h
 header-y += fixed_code.h