doc: update kptr_restrict documentation

Recently the behaviour of printk specifier %pK was changed. The
documentation does not currently mirror this.

Update documentation for sysctl kptr_restrict.
Signed-off-by: NTobin C. Harding <me@tobin.cc>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/sysctl/kernel.txt

@@ -391,7 +391,8 @@ kptr_restrict:
 This toggle indicates whether restrictions are placed on
 exposing kernel addresses via /proc and other interfaces.
 
-When kptr_restrict is set to (0), the default, there are no restrictions.
+When kptr_restrict is set to 0 (the default) the address is hashed before
+printing. (This is the equivalent to %p.)
 
 When kptr_restrict is set to (1), kernel pointers printed using the %pK
 format specifier will be replaced with 0's unless the user has CAP_SYSLOG