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>

arch/blackfin/kernel/ptrace.c

@@ -114,8 +114,8 @@ put_reg(struct task_struct *task, long regno, unsigned long data)
 /*
  * check that an address falls within the bounds of the target process's memory mappings
  */
-static inline int is_user_addr_valid(struct task_struct *child,
-				     unsigned long start, unsigned long len)
+int
+is_user_addr_valid(struct task_struct *child, unsigned long start, unsigned long len)
 {
 	struct vm_area_struct *vma;
 	struct sram_list_struct *sraml;