Revert "stackprotector: Increase the per-task stack canary's random range from...

Revert "stackprotector: Increase the per-task stack canary's random range from 32 bits to 64 bits on 64-bit platforms"

This reverts commit 609a3e81 which is
commit 5ea30e4e58040cfd6434c2f33dc3ea76e2c15b05 upstream.

It shouldn't have been backported to 3.18, as we do not have
get_random_long() in that kernel tree.

Reported-by: Philip Müller <philm@manjaro.org>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arjan van Ven <arjan@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-hardening@lists.openwall.com
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>