kill strlen_user()

no callers, no consistent semantics, no sane way to use it...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/tile/include/asm/uaccess.h

@@ -327,7 +327,6 @@ extern unsigned long raw_copy_in_user(
 
 
 extern long strnlen_user(const char __user *str, long n);
-extern long strlen_user(const char __user *str);
 extern long strncpy_from_user(char *dst, const char __user *src, long);
 
 /**